Zoom image pickup apparatus

ABSTRACT

A zoom image pickup apparatus includes a mount portion, a zoom lens which forms an image of light incident from the mount portion, and an image pickup element which is disposed at an image forming position, wherein the zoom lens includes in order from an object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power, and the fourth lens unit is a focusing lens unit, and at the time of zooming from a wide angle end to a telephoto end, only the second lens unit and the fourth lens unit move, and the following conditional expression (1) is satisfied: 
       φ L1 &lt;φ 3GL1   (1).

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application of InternationalApplication No. PCT/JP2015/053641 filed on Feb. 10, 2015, which claimspriority to International Application No. PCT/JP2015/053641; the entirecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a zoom image pickup apparatus which canbe connected to an eyepiece portion of an optical instrument.

Description of the Related Art

Optical instruments include endoscopes, microscopes, telescopes, andbinoculars for example. In an endoscope for instance, often, images of asite to be observed are acquired by attaching an adapter and a videocamera to an eyepiece portion of the endoscope. Images acquired are usedfor diagnosis and treatment of the site to be observed. Moreover, imagesacquired are recorded in a recording medium.

A camera such as a television camera and a film camera is used forimaging. Recently in particular, the imaging is carried out by asmall-size television camera in which a solid image pickup element suchas a CCD (charge coupled device) is used. An endoscope image that ispicked up is displayed on a television monitor for example. In manycases, diagnosis and treatment are carried out by using the endoscopeimage displayed.

With the recent advancement in semiconductor technology, small-sizing ofelements and high-densification of pixels have been carried out forimage pickup elements to be used in these television cameras. Therefore,an optical system to be used in combination with such image pickupelement also has to have a high optical performance.

As mentioned above, in an endoscope, an adapter and a television cameraare to be attached to an eyepiece portion of the endoscope. In sucharrangement, an image formed by an eyepiece of the endoscope is formedon an image pickup element provided inside the television camera, via animage pickup optical system in the adapter.

In actual image pickup, different adapters of various types withdifferent magnification are provided, and the adapters are to be usedproperly according to the type and purpose of the endoscope to be used.For this, a large number of adapters are necessary and the cost becomeshigh.

Moreover, when a size of a site to be observed is to be changed bychanging the magnification while in use, the adapter is to be replacedevery time. However, it is difficult to replace the adapter duringsurgery for example. Moreover, it is practically difficult to adjust asize of an image of a site to be observed to a size desired by a user(such as a person performing the surgery). Consequently, with regard tothe size of the image, the user has to compromise to certain extent.

As a method for achieving an image of a size desired by the user, amethod of using a zooming optical system for the optical system insidethe adapter is available. In a plurality of endoscopes, when eachendoscope has same diopter scale, an object-point position with respectto the adapter is same for any endoscope. Consequently, even when theoptical system inside the adapter is a zooming optical system, there isno need to provide a focusing mechanism.

However, obviously there are cases in which the diopter scale of eachendoscope differs. For example, in rigid endoscopes, diopter scalediffers in each rigid endoscope in many cases. Even in flexibleendoscopes, obviously there are cases in which the diopter scale of eachflexible endoscope differs.

When the diopter scale differs for each endoscope, the diopter scalevaries according to an object position. Therefore, when the endoscope tobe combined with a zooming optical system differs, in a case in whichthe diopter scale thereof differs according to a distance up to a siteto be observed, it is necessary to provide a focusing mechanism to thezooming optical system.

Although the abovementioned description has been made by citing anexample of endoscopes, a point of differing diopter scales is similarfor microscope, telescopes, and binoculars.

As a focusing method, there is a method of moving the whole zoomingoptical system in an optical direction. In video photography, capturingis carried out while zooming and focusing all the time. When the zoomingand focusing are carried out all the time, a focusing speed depends on aweight of lenses. Moreover, as an overall length of lenses varies at thetime of focusing, the optical system and an overall image pickupapparatus become large.

In view of the abovementioned circumstances, a zooming optical system inwhich the focusing speed is increased by moving a comparatively smalllens and the overall optical system is made compact has been proposed.Such zooming optical systems have been proposed in Japanese PatentApplication Laid-open Publication No. Hei 9-325273 and Japanese PatentApplication Laid-open Publication No. Hei 11-125770 respectively.

The zooming optical system disclosed in Japanese Patent ApplicationLaid-open Publication No. Hei 9-325273 includes in order from an objectside, a first unit having a positive refractive power, a second unithaving a negative refractive power, and a third unit having a positiverefractive power. The first unit is a focusing lens unit, and a diopterscale adjustment from a positive refractive power to a negativerefractive power is possible by the movement of the focusing lens unit.

The zooming optical system disclosed in Japanese Patent ApplicationLaid-open Publication No. Hei 11-125770 includes in order from an objectside, a first lens unit having a positive refractive power, a secondlens unit having a negative refractive power, a third lens unit having apositive refractive power, and a fourth lens unit. The first lens unitis a focusing lens unit, and the whole lens unit or some of the lensesin the lens unit move in an optical axial direction.

SUMMARY OF THE INVENTION

A zoom image pickup apparatus according to the present inventioncomprises,

a mount portion,

a zoom lens which forms an image of light incident from the mountportion, and

an image pickup element which is disposed at an image forming position,wherein

the zoom lens includes in order from an object side,

a first lens unit having a positive refractive power,

a second lens unit having a negative refractive power,

a third lens unit having a positive refractive power,

a fourth lens unit having a negative refractive power, and

a fifth lens unit having a positive refractive power, and

the fourth lens unit is a focusing lens unit, and

at a time of zooming from a wide angle end to a telephoto end, at leastthe second lens unit and the fourth lens unit move, and

at the wide angle end when focused to a first object, the followingconditional expression (1) is satisfied:

φ_(L1)<φ_(3GL1)  (1)

where,

φ_(L1) denotes an effective diameter of a lens surface positionednearest to object of the zoom lens,

φ_(3GL1) denotes an effective diameter of a lens surface positionednearest to object of the third lens unit,

the first object is an object when an object-point distance is 1000 mm,here

the object-point distance is a distance from a lens surface positionednearest to object of the zoom lens, up to the object, and

the effective diameter is the maximum diameter of a range on a targetlens surface, through which a light ray contributing to image formationpasses.

Moreover, another zoom image pickup apparatus according to the presentinvention comprises,

a mount portion,

a zoom lens which forms an image of light incident from the mountportion, and

an image pickup element which is disposed at an image forming position,wherein

the zoom lens includes in order from an object side,

a first lens unit having a positive refractive power,

a second lens unit having a negative refractive power,

a third lens unit having a positive refractive power,

a fourth lens unit having a negative refractive power, and

a fifth lens unit having a positive refractive power, and

the fourth lens unit is a focusing lens unit, and

at a time of zooming from a wide angle end to a telephoto end, only thesecond lens unit and the fourth lens unit move, and the first lens unit,the third lens unit, and the fifth lens unit are fixed, and

the following conditional expression (13) is satisfied:

|(y _(w7d′) −y _(w7d))/P|/(1/N)<250  (13)

where,

a side of the mount portion is let to be an object side and a side ofthe image pickup element is let to be an image side,

each of y_(w7d) and y_(w7d)′ is a height of a predetermined light ray ata position at which the predetermined light ray intersects an imageplane, and y_(w7d) denotes a light-ray height when focused to the firstobject and y_(w7d′) denotes a light-ray height in a defocused state,here

the defocused state is a state in which the focusing lens unit is movedby Δ_(s2) when focused to the first object, and Δ_(s2)=10×P,

0.0008<P<0.005,0.05<1/N<1,

where,

N denotes the number of pixels (unit millions of pixels) of the imagepickup element,

P denotes a pixel pitch (unit mm) of the image pickup element,

the predetermined light ray is a light ray with an angle of view of 7degrees at the wide angle end, which passes through a center of a lenssurface nearest to object of the zoom lens,

the first object is an object when an object-point distance is 1000 mm,here

the object-point distance is a distance from a lens surface positionednearest to object of the zoom lens, up to the object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B are diagrams for explaining y_(w7d) and y_(w7d′);

FIG. 2A, FIG. 25, and FIG. 2C are cross-sectional views along an opticalaxis showing an optical arrangement at the time of focusing to a firstobject, of a zoom lens according to an example 1;

FIG. 3A, FIG. 3B, FIG. 3C, FIG. 3D, FIG. 3E, FIG. 3F, FIG. 3G, FIG. 3H,FIG. 3I, FIG. 3J, FIG. 3K, and FIG. 3L are aberration diagrams at thetime of focusing to the first object, of the zoom lens according to theexample 1;

FIG. 4A, FIG. 4B, and FIG. 4C are cross-sectional views along an opticalaxis showing an optical arrangement at the time of focusing to a firstobject, of a zoom lens according to an example 2;

FIG. 5A, FIG. 5B, FIG. 5C, FIG. 5D, FIG. 5E, FIG. 5F, FIG. 5G, FIG. 5H,FIG. 5I, FIG. 5J, FIG. 5K, and FIG. 5L are aberration diagrams at thetime of focusing to the first object, of the zoom lens according to theexample 2;

FIG. 6A, FIG. 6B, and FIG. 6C are cross-sectional views along an opticalaxis showing an optical arrangement at the time of focusing to a firstobject, of a zoom lens according to an example 3;

FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, FIG. 7E, FIG. 7F, FIG. 7G, FIG. 7H,FIG. 7I, FIG. 7J, FIG. 7K, and FIG. 7L are aberration diagrams at thetime of focusing to the first object, of the zoom lens according to theexample 3;

FIG. 8A, FIG. 8B, and FIG. 8C are cross-sectional views along an opticalaxis showing an optical arrangement at the time of focusing to a firstobject, of a zoom lens according to an example 4;

FIG. 9A, FIG. 9B, FIG. 9C, FIG. 9D, FIG. 9E, FIG. 9F, FIG. 9G, FIG. 9H,FIG. 9I, FIG. 9J, FIG. 9K, and FIG. 9L are aberration diagrams at thetime of focusing to the first object, of the zoom lens according to theexample 4;

FIG. 10A, FIG. 10B, and FIG. 100 are cross-sectional views along anoptical axis showing an optical arrangement at the time of focusing to afirst object, of a zoom lens according to an example 5;

FIG. 11A, FIG. 11B, FIG. 11C, FIG. 11D, FIG. 11E, FIG. 11F, FIG. 11G,FIG. 11H, FIG. 11I, FIG. 11J, FIG. 11K, and FIG. 11L are aberrationdiagrams at the time of focusing to the first object, of the zoom lensaccording to the example 5;

FIG. 12A, FIG. 125, and FIG. 12C are cross-sectional views along anoptical axis showing an optical arrangement at the time of focusing to afirst object, of a zoom lens according to an example 6;

FIG. 13A, FIG. 13B, FIG. 13C, FIG. 13D, FIG. 13E, FIG. 13F, FIG. 13G,FIG. 13H, FIG. 13I, FIG. 13J, FIG. 13K, and FIG. 13L are aberrationdiagrams at the time of focusing to the first object, of the zoom lensaccording to the example 6;

FIG. 14A, FIG. 14B, and FIG. 14C are cross-sectional views along anoptical axis showing an optical arrangement at the time of focusing to afirst object, of a zoom lens according to an example 7;

FIG. 15A, FIG. 15B, FIG. 15C, FIG. 15D, FIG. 15E, FIG. 15F, FIG. 15G,FIG. 15H, FIG. 15I, FIG. 15J, FIG. 15K, and FIG. 15L are aberrationdiagrams at the time of focusing to the first object, of the zoom lensaccording to the example 7;

FIG. 16A, FIG. 16B, and FIG. 16C are cross-sectional views along anoptical axis showing an optical arrangement at the time of focusing to afirst object, of a zoom lens according to an example 8;

FIG. 17A, FIG. 17B, FIG. 17C, FIG. 170, FIG. 17E, FIG. 17F, FIG. 17G,FIG. 17H, FIG. 17I, FIG. 17J, FIG. 17K, and FIG. 17L are aberrationdiagrams at the time of focusing to the first object, of the zoom lensaccording to the example 8;

FIG. 18A, FIG. 185, and FIG. 180 are cross-sectional views along anoptical axis showing an optical arrangement at the time of focusing to afirst object, of a zoom lens according to an example 9;

FIG. 19A, FIG. 19B, FIG. 19C, FIG. 19D, FIG. 19E, FIG. 19F, FIG. 19G,FIG. 19H, FIG. 19I, FIG. 19J, FIG. 19K, and FIG. 19L are aberrationdiagrams at the time of focusing to the first object of the zoom lensaccording to the example 9; and

FIG. 20 is a diagram showing how a zoom image pickup apparatus of thepresent embodiment is connected to an optical instrument.

DETAILED DESCRIPTION OF THE INVENTION

A zoom image pickup apparatus according to the present embodimentincludes a mount portion, a zoom lens which forms an image of lightincident from the mount portion, and an image pickup element which isdisposed at an image forming position, wherein the zoom lens includes inorder from an object side, a first lens unit having a positiverefractive power, a second lens unit having a negative refractive power,a third lens unit having a positive refractive power, a fourth lens unithaving a negative refractive power, and a fifth lens unit having apositive refractive power, and the fourth lens unit is a focusing lensunit, and at a time of zooming from a wide angle end to a telephoto end,at least the second lens unit and the fourth lens unit move, and at thewide angle end when focused to a first object, the following conditionalexpression (1) is satisfied:

φ_(L1)<φ_(3GL1)  (1)

where,

φ_(L1) denotes an effective diameter of a lens surface positionednearest to object of the zoom lens,

φ_(3GL1) denotes an effective diameter of a lens surface positionednearest to object of the third lens unit,

the first object is an object when an object-point distance is 1000 mm,here

the object-point distance is a distance from a lens surface positionednearest to object of the zoom lens, up to the object, and

the effective diameter is the maximum diameter of a range on a targetlens surface, through which a light ray contributing to image formationpasses.

In the zoom image pickup apparatus of the present embodiment, the zoomlens includes in order from the object side, the first lens unit havinga positive refractive power, the second lens unit having a negativerefractive power, the third lens unit having a positive refractivepower, the fourth lens unit having a negative refractive power, and thefifth lens unit having a positive refractive power.

The zoom lens arranged in such manner can be used as an image pickupoptical system for endoscope. When an image pickup optical system forendoscope is combined with an endoscope optical system, anentrance-pupil position is restricted. Generally, an image pickupoptical system for endoscope does not have an aperture stop. Therefore,an aperture of an image-forming light beam is determined by anexit-pupil diameter of the endoscope optical system. An eye-point of anendoscope optical system is a position where generally there is noproblem for visual observation, such as a position few mm away from aneyepiece end surface.

Since the first lens unit is near the exit-pupil position of theendoscope optical system, an outer diameter of the first lens unitbecomes small. In this case, since the first lens unit becomessmall-sized, from size point of view, the first lens unit becomes acandidate for the focusing lens unit.

However, the first lens unit is a lens unit which is effective forcorrection of a spherical aberration. Exerting the effect for correctionof the spherical aberration signifies that the first lens unit is a lensunit which substantially affects the spherical aberration. Therefore,when the first lens unit is let to be the focusing lens unit, thespherical aberration fluctuates substantially with the movement of thelens unit.

Therefore, the fourth lens unit is let to be the focusing lens unit. Bymaking such arrangement, a position of the lens unit that moves becomesaway from the exit-pupil position of the endoscope optical system.Moreover, since the refractive power of the third lens unit is apositive refractive power, it is possible to suppress a height of alight ray at the fourth lens unit to be low. As a result of this, it ispossible to suppress the fluctuation in the spherical aberration at thetime of focusing.

Furthermore, by letting the refractive power of the focusing lens unitto be a negative refractive power, it is possible to make a focusingsensitivity high. As a result of this, it is possible to suppress anincrease in the amount of movement of the focusing lens unit at the timeof focusing.

Furthermore, the fifth lens unit is disposed on the image side of thefourth lens unit, and the refractive power of the fifth lens unit is letto be a positive refractive power. In this case, since the fifth lensunit functions as a reduction optical system, it is possible to makesmall an aberration fluctuation at the time of focusing, in the fifthlens unit.

Moreover, since a substantial zooming effect emanates by the second lensunit and the third lens unit, the second lens unit and the third lensunit become the main variator. Here, when the focusing lens unit ispositioned on the object side of the main variator, an amount ofvariation in the image height and an amount of variation in the imageposition due to the movement of the focusing lens unit varysubstantially according to the movement of the main variator. In suchmanner, the variation in the image height and the variation in the imageposition due to the movement of the focusing lens unit are affectedsubstantially by a state of the movement of the main variator.

For this reason, by letting the fourth lens unit to be the focusing lensunit, the focusing lens unit is disposed next to the main variator.Consequently, since an effect of the main variator can be ignored, thefocusing sensitivity ceases to vary substantially. Moreover, since thevariation in the focusing sensitivity being small, it becomes easy tocontrol the movement of the focusing lens unit.

Moreover, by satisfying conditional expression (1), since the effectivediameter of the third lens unit on the image side of first lens unit ismade large, it becomes easy to reduce vignetting of an off-axis lightbeam reaching an image pickup surface when the zoom lens is connected toan eyepiece portion of an endoscope etc.

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that the following conditional expression(2) be satisfied:

−4.5<f ₄ /f ₅<−0.2  (2)

where,

f₄ denotes a focal length of the fourth lens unit, and

f₅ denotes a focal length of the fifth lens unit.

Conditional expression (2) is a conditional expression which regulates aratio of the refractive power of the fourth lens unit and the refractivepower of the fifth lens unit. By satisfying conditional expression (2),it is possible to set appropriately each of the refractive power of thefourth lens unit and the refractive power of the fifth lens unit.Consequently, in the fifth lens unit, it is possible to correctfavorably an aberration which occurs in the fourth lens unit. As aresult of this, it is possible to maintain a favorable opticalperformance in the zoom lens.

The refractive power of the fourth lens unit being a negative refractivepower, a light ray emerged from the fourth lens unit advances to bemoving away from an optical axis. By exceeding a lower limit value ofconditional expression (2), even an aberration which occurs due to thelight ray advancing to be moving away from the optical axis can becorrected favorably in the fifth lens unit. It is possible to carry outfavorably a correction of a coma in particular.

By falling below an upper limit value of conditional expression (2), itis possible to carry out an aberration correction favorably whilemaintaining appropriately the refractive power of the fourth lens unit.Moreover, falling of value below the upper limit value is effective forshortening an overall length of the optical system.

It is preferable that the following conditional expression (2′) besatisfied instead of conditional expression (2).

−2.5<f ₄ /f ₅<−0.3  (2′)

Furthermore, it is more preferable that the following conditionalexpression (2″) be satisfied instead of conditional expression (2).

−1.6<f ₄ /f ₅<−0.5  (2″)

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that the following conditional expression(3) be satisfied:

0.55<|β_(ctw)|<5  (3)

where,

β_(ctw)=(1−β_(fcw)×β_(fcw))×β_(w)′×β_(w)′,here

each of β_(fcw) and β_(w)′ is a lateral magnification at the wide angleend when focused to the first object, and β_(fcw) denotes a lateralmagnification of the fourth lens unit and β_(w)′ denotes a lateralmagnification of a lens unit positioned on an image side of the fourthlens unit,

the first object is an object when the object-point distance is 1000 mm,and

the object-point distance is a distance from a lens surface positionednearest to object of the zoom lens up to an object.

Conditional expression (3) is a conditional expression related to thefocusing sensitivity at the wide angle end. As mentioned above, thefocusing sensitivity is the amount indicating the amount of movement ofthe image plane with respect to the amount of movement of the focusinglens unit.

By exceeding a lower limit value of conditional expression (3), it ispossible to suppress the increase in the amount of movement of thefocusing lens unit at the time of focusing. As a result of this, it ispossible to suppress the fluctuation in an astigmatism at the time offocusing. Moreover, since it is possible to suppress the increase in theamount of movement of the focusing lens unit, it is possible to makesmall a space for the movement of the focusing lens unit. As a result ofthis, it is possible to carry out small-sizing of the zoom lens andsmall-sizing of the zoom image pickup apparatus.

By falling below an upper limit value of conditional expression (3), itis possible to suppress the astigmatism from occurring in the focusinglens unit.

It is preferable that the following conditional expression (3′) besatisfied instead of conditional expression (3).

0.555<|β_(ctw)|<4  (3′)

Furthermore, it is more preferable that the following conditionalexpression (3″) be satisfied instead of conditional expression (3).

0.555<|β_(ctw)|<3  (3″)

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that a lens unit having a negativerefractive power which satisfies the following conditional expression(4) is positioned on the object side of a lens unit having a positiverefractive power:

0.1<d _(ng) /d _(pg)<0.9  (4)

where,

each of d_(ng) and d_(pg) is a thickness on an optical axis of a lensunit, and

d_(ng) denotes a thickness of a lens unit having the largest negativerefractive power from among thicknesses of lens units positioned on theobject side of the fourth lens unit, and

d_(pg) denotes a thickness of the lens unit having the largest positiverefractive power from among thicknesses of lens units positioned on theobject side of the fourth lens unit.

Conditional expression (4) is a conditional expression related to aratio of the thickness on the optical axis of the two lens units. One isa thickness of a predetermined positive lens unit and the other is athickness of a predetermined negative lens unit. The predeterminedpositive lens unit is a lens unit having the largest positive refractivepower from among the lens units positioned on the object side of thefourth lens unit. The predetermined negative lens unit is a lens unithaving the largest negative refractive power from among the lens unitspositioned on the object side of the fourth lens unit.

When the lens units are arranged in order of the lens unit having anegative refractive power and the lens unit having a positive refractivepower, from the object side, a light ray is diverged at the lens unithaving the negative refractive power. In this case, the lens unit havinga positive refractive power is sought to correct an aberration at aposition at which the height of a light ray is high. Particularly, sincea diameter of a light beam becomes large for an axial light beam, thelens unit having a positive refractive power is sought to correct thespherical aberration. Conditional expression (4) is a conditionalexpression for correcting the spherical aberration favorably whilesuppressing an increase in the overall length of the optical system.

By exceeding a lower limit value of conditional expression (4), it ispossible to shorten the overall length of the optical system. By fallingbelow an upper limit value of conditional expression (4), it is possibleto carry out the correction of the spherical aberration favorably.

It is preferable that the following conditional expression (4′) besatisfied instead of conditional expression (4).

0.15<d _(ng) /d _(pg)<0.7  (4′)

Furthermore, it is more favorable that the following conditionalexpression (4″) be satisfied instead of conditional expression (4).

0.17<d _(ng) /d _(pg)<0.55  (4″)

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that the following conditional expression(5) be satisfied:

1<φ_(fc)/φ_(L1)<3  (5)

where,

each of φ_(fc) and φ_(L1) is an effective diameter at the wide angle endwhen focused to the first object, and

φ_(fc) denotes an effective diameter of a lens surface positionednearest to object of the focusing lens unit,

φ_(L1) denotes the effective diameter of a lens surface positionednearest to object of the zoom lens,

the first object is an object when an object-point distance is 1000 mm,where

the object-point distance is the distance from the lens surfacepositioned nearest to object of the zoom lens, up to the object, and

the effective diameter is the maximum diameter of a range on a targetlens surface, through which a light ray contributing to image formationpasses.

Conditional expression (5) is a conditional expression related to aratio of two effective diameters. One is the effective diameter of thelens surface positioned nearest to object in the focusing lens unit andthe other is the effective diameter of the lens surface positionednearest to object in the zoom lens. It is preferable to set theeffective diameter of the zoom lens for achieve both of guiding anoptical path of an exit pupil to the image pickup element withoutvignetting or with small vignetting, and small-sizing.

By exceeding a lower limit value of conditional expression (5), it ispossible to prevent the first lens unit from becoming large-sized. Insuch manner, exceeding the lower limit value of conditional expression(5) is advantageous for small-sizing of the optical system. As a result,it is possible to carry out the correction of the spherical aberrationfavorably while achieving the small-sizing of the optical system.

By falling below an upper limit value of conditional expression (5), itis possible to carry out the correction of the spherical aberration andcoma in the focusing lens unit while preventing the focusing lens unitfrom becoming large-sized.

It is preferable that the following conditional expression (5′) besatisfied instead of conditional expression (5).

1<φ_(fc)/φ_(L1)<2.5  (5′)

Furthermore, it is more preferable that the following conditionalexpression (5″) be satisfied instead of conditional expression (5).

1.1<φ_(fc)/φ_(L1)<2  (5″)

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that the following conditional expression(6) be satisfied:

−4<f ₄ /f _(LW)<−0.4  (6)

where,

f₄ denotes a focal length of the fourth lens unit,

f_(Lw) denotes a focal length at the wide angle end of the zoom lenswhen focused to the first object,

the first object is an object when an object-point distance is 1000 mm,and

the object-point distance is a distance from a lens surface positionednearest to object of the zoom lens up, to the object.

Conditional expression (6) is a conditional expression in which a ratioof two focal lengths is taken. One is the focal length of the fourthlens unit and the other is the focal length of the zoom lens. The focallength of the zoom lens is a focal length at the wide angle end whenfocused to the first object.

By exceeding a lower limit value of conditional expression (6), since itis possible to set favorably Petzval sum for the fourth lens unit, it ispossible to correct the astigmatism favorably. Accordingly, it ispossible to maintain a favorable optical performance.

It is effective to fall below an upper limit value of conditionalexpression (6) for shortening the overall length of the optical system,and accordingly, it is possible to make small the amount of movement ofthe fourth lens unit.

It is preferable that the following conditional expression (6′) besatisfied instead of conditional expression (6).

−3<f ₄ /f _(Lw)<−0.5  (6′)

Furthermore, it is more preferable that the following conditionalexpression (6″) be satisfied instead of conditional expression (6).

−1.2<f ₄ /f _(Lw)<−0.7  (6″)

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that the following conditional expression(7) be satisfied:

1<f ₅ /f _(Lw)<3  (7)

where,

f₅ denotes the focal length of the fifth lens unit,

f_(Lw) denotes the focal length at a wide angle end of the zoom lenswhen focused to the first object, and

the first object is an object when an object-point distance is 1000 mm,here

the object-point distance is a distance from a lens surface positionednearest to object of the zoom lens, up to the object.

Conditional expression (7) is a conditional expression in which a ratioof two focal lengths is taken. One is the focal length of the fifth lensunit and the other is the focal length of the zoom lens unit. The focallength of this zoom lens is a focal length at the wide angle end whenfocused to the first object.

In the fifth lens unit, an aberration which occurs due to an off-axislight ray can be corrected favorably. Moreover, imparting an appropriaterefractive power to the fifth lens unit is effective for shortening theoverall length of the optical system.

By exceeding a lower limit value of conditional expression (7), it ispossible to correct the coma favorably. By falling below an upper limitvalue of conditional expression (7), it is possible to achieveshortening of the overall length of the optical system.

It is preferable that the following conditional expression (7′) besatisfied instead of conditional expression (7)

1<f ₅ /f _(Lw)<2.7  (7′)

Furthermore, it is more preferable that the following conditionalexpression (7″) be satisfied instead of conditional expression (7).

1.1<f ₅ /f _(Lw)<2.2  (7″)

Moreover, in the zoom image pick apparatus according to the presentembodiment, it is preferable that the following conditional expression(8) be satisfied:

−5<f _(ng) /f _(pg)<−0.5  (8)

where,

f_(ng) denotes a focal length of a lens having the largest negativerefractive power from among focal lengths of lens units positioned onthe object side of the fourth lens unit, and

f_(pg) denotes a focal length of a lens having the largest positiverefractive power from among focal lengths of lens units positioned onthe object side of the fourth lens unit.

Conditional expression (8) is a conditional expression related to aratio of the focal lengths of the two lens units. One is the focallength of the predetermined negative lens unit and the other is thefocal length of the predetermined positive lens unit. The predeterminednegative lens unit is the lens unit having the largest negativerefractive power from among the lens units positioned on the object sideof the fourth lens unit. The predetermined positive lens unit is thelens unit having the largest positive refractive power from among thelens unit positioned on the object side of the fourth lens unit.

For example, the second lens unit corresponds to the predeterminednegative lens unit, and the third lens unit corresponds to thepredetermined positive lens unit. In this case, conditional expression(8) becomes a conditional expression related to a ratio of the focallengths of the second lens unit and the focal lengths of the third lensunit.

By satisfying conditional expression (8), it is possible to balance therefractive power of the predetermined negative lens unit and therefractive power of the predetermined positive lens unit. In this case,since it is possible to set Petzval sum favorably, it is possible tocorrect the astigmatism favorably. Accordingly, it is possible tomaintain a favorable optical performance.

It is preferable that the following conditional expression (8′) beinstead of conditional expression (8).

−4<f _(ng) /f _(pg)<−0.9  (8′)

Furthermore, it is more preferable that the following conditionalexpression (8″) be satisfied instead of conditional expression (8).

−3.5<f _(ng) f _(pg)<−1  (8″)

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that only the fourth lens unit move at thetime of focusing, and the following conditional expression (9) besatisfied:

0.8<|β_(ctt)|/|β_(ctw)|<1.8  (9)

where,

β_(ctt)=(1−β_(fct)×β_(fct))×β_(t)′×β_(t)′,

β_(ctw)=(1−β_(fcw)×β_(fcw))×β_(w)′×β_(w)′, here

each of β_(fct) and β_(t)′ is a lateral magnification at the telephotoend when focused to the first object, and β_(fct) denotes a lateralmagnification of the fourth lens unit and β_(t)′ denotes a lateralmagnification of a lens unit positioned on an image side of the fourthlens unit,

each of β_(fcw) and β_(w)′ is the lateral magnification at the wideangle end when focused to the first object, and β_(fcw) denotes thelateral magnification of the fourth lens unit and β_(w)′ denotes thelateral magnification of a lens unit positioned on an image side of thefourth lens unit, and

the first object is an object when the object-point distance is 1000 mm,here

the object-point distance is a distance from a lens surface positionednearest to object of the zoom lens up to an object.

Conditional expression (9) is a conditional expression related to aratio of the focusing sensitivity at the telephoto end and the focusingsensitivity at the wide angle end. As mentioned above, the focusingsensitivity is the amount indicating the amount of movement of the imageplane with respect to the amount of movement of the focusing lens unit.

When conditional expression (9) is satisfied, the fluctuation in thefocusing sensitivity is suppressed at both the telephoto end and thewide angle end. In such manner, since the variation in the focusingsensitivity being small, the amount of movement of the image plane withrespect to the amount of movement of the focusing lens unit does notvary substantially according to a state. Consequently, it becomes easyto control the movement of the focusing lens unit.

It is preferable that the following conditional expression (9′) besatisfied instead of conditional expression (9)

0.9<|β_(ctt)|/|β_(ctw)|<1.5  (9′)

Furthermore, it is more preferable that the following conditionalexpression (9″) be satisfied instead of conditional expression (9).

0.9<|β_(ctt)|/|β_(ctw)|<1.2  (9″)

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that the following conditional expression(10) be satisfied:

0.03<φ_(L1) /f _(Lt)<0.2  (10)

where,

φ_(L1) is the effective diameter of a lens surface positioned nearest toobject of the zoom lens, and denotes an effective diameter at the wideangle end when focused to the first object,

f_(Lt) denotes a focal length at the telephoto end of the zoom lens whenfocused to the first object,

the first object is an object when an object-point distance is 1000 mm,where

the object-point distance is the distance from the lens surfacepositioned nearest to object of the zoom lens, up to the object, and

the effective diameter is the maximum diameter of a range on a targetlens surface, through which a light ray contributing to image formationpasses.

Conditional expression (10) is a conditional expression in which a ratioof the effective diameter of the lens surface positioned nearest to theobject of the zoom lens and the focal length of the zoom lens at thetelephoto end when focused to the first object is taken. The effectivediameter of a lens is the maximum diameter of a range through which alight contributing to image formation at the wide angle end when focusedto the first object passes, or in other words, is a diameter regulatedby a marginal ray.

When conditional expression (10) is satisfied, since it is possible tomake small the effective diameter of the lens surface positioned nearestto object of the zoom lens, it is possible to achieve small-sizing ofthe optical system.

It is preferable that the following conditional expression (10′) besatisfied instead of conditional expression (10).

0.04<φ_(L1) /f _(1t)<0.18  (10′)

Furthermore, it is more preferable that the following conditionalexpression (10″) be satisfied instead of conditional expression (10).

0.05<φ_(L1) /f _(1t)<0.15  (10″)

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that, at the time of zooming, only thesecond lens unit and the fourth lens unit move, and the first lens unit,the third lens unit, and the fifth lens unit be fixed.

A lens unit having a positive refractive power is disposed on the objectside of the second lens unit and the object side of the fourth lensunit. Since light rays are converged at a position of the second lensunit and a position of the fourth lens unit, it is possible to make thesecond lens unit and the fourth lens unit small-sized. Therefore, byletting the second lens unit and the fourth lens unit to be movable lensunits, it is possible to arrange the whole optical system to besmall-sized. Moreover, since the number of movable lens units is let tobe two, it is possible to make a mechanical arrangement and a control ofthe movable lens units comparatively simple.

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that the third lens unit include a positivelens which is disposed nearest to object and a cemented lens which isdisposed nearest to image.

When an image pickup optical system for endoscope is combined with anendoscope optical system, the entrance-pupil position is restricted.Generally, an image pickup optical system for endoscope does not have anaperture stop. Therefore, an aperture of an image-forming light beam isdetermined by an exit-pupil diameter of the endoscope optical system. Aneye-point of an endoscope optical system is a position where generallythere is no problem for visual observation, such as a position few mmaway from an eyepiece end surface.

A light ray incident on the third lens unit is diverged at the secondlens unit having a negative refractive power. Since a height of an axiallight ray in the third lens unit becomes high, correction of a sphericalaberration becomes difficult. For this reason, a positive lens of whichboth sides are air-contact surfaces is to be disposed nearest to object.Accordingly, since bending becomes possible at two air-contact surfaces,it is possible to correct the spherical aberration favorably. Moreover,by disposing the cemented lens nearest to image, it is possible tocorrect favorably a longitudinal chromatic aberration.

Moreover, at least one cemented surface having a negative refractivepower may further be provided in the third lens unit. By making sucharrangement, it is possible to correct an astigmatism favorably.

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that a rearmost lens unit be disposednearest to image, and the rearmost lens unit include a positive lenswhich is disposed nearest to object, and a negative lens which isdisposed nearest to image.

The rearmost lens unit is a lens unit disposed nearest to image in thezoom lens. In the rearmost lens unit, by disposing the lenses in orderof the positive lens and the negative lens from the object side, it ispossible to diverge by the negative lens a light ray that was convergedby the positive lens. As a result of this, it is possible to make gentlean angle of a light ray passing through the rearmost lens unit, withrespect to the optical axis. Therefore, it is possible to suppress anoccurrence of an off-axis aberration in particular.

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that the following conditional expression(11) be satisfied:

−5<(r _(4Gff) +r _(4Gfb))/(r _(4Gff) −r _(4Gfb))<5  (11)

where,

r_(4Gff) denotes a radius of curvature of an object-side lens surface ofa lens positioned nearest to object in the fourth lens unit, and

r_(4Gfb) denotes a radius of curvature of an image-side lens surface ofa lens positioned nearest to image in the fourth lens unit.

Conditional expression (11) is a conditional expression related to ashape of the focusing lens unit. When conditional expression (11) issatisfied, the shape of the focusing lens unit becomes a shape suitablefor correcting the spherical aberration. Therefore, it is possible tosuppress a fluctuation in the spherical aberration at the time offocusing.

Moreover, it is preferable that the following conditional expression(11′) be satisfied instead of conditional expression (11).

−4<(r _(4Gff) +r _(4Gfb))/(r _(4Gff) −r _(4Gfb))<4  (11′)

Furthermore, it is more preferable that the following conditionalexpression (11″) be satisfied instead of conditional expression (11).

−3<(r _(4Gff) +r _(4Gfb))/(r _(4Gff) −r _(4Gfb))<2  (11″)

Moreover, in the zoom image pickup apparatus according to the presentembodiment, it is preferable that the following conditional expression(12) be satisfied:

−5<(r _(1f) +r _(1b))/(r _(1f) −r _(1b))<5  (12)

where,

r_(1f) denotes a radius of curvature of an object-side lens surface of alens positioned nearest to image, and

r_(1b) denotes a radius of curvature of an image-side lens surface of alens positioned nearest to image.

Conditional expression (12) is a conditional expression related to ashape of a lens positioned nearest to image.

By exceeding a lower limit value of conditional expression (12), it ispossible to correct the astigmatism favorably. As a result of this, itis possible to maintain a favorable optical performance. By fallingbelow an upper limit value of conditional expression (12), it ispossible to correct the spherical aberration favorably. As a result ofthis, it is possible maintain a favorable optical performance.

Moreover, it is preferable that the following conditional expression(12′) be satisfied instead of conditional expression (12).

−3<(r _(1f) +r _(1b))/(r _(1f) −r _(1b))<3  (12′)

Furthermore, it is more preferable that the following conditionalexpression (12″) be satisfied instead of conditional expression (12).

−2<(r _(1f) +r _(1b))/(r _(1f) −r _(1b))<2  (12″)

Moreover, a zoom image pickup apparatus according to the presentembodiment includes amount portion, a zoom lens which forms an image oflight incident from the mount portion, and an image pickup element whichis disposed at an image forming position, wherein the zoom lens includesin order from an object side, a first lens unit having a positiverefractive power, a second lens unit having a negative refractive power,a third lens unit having a positive refractive power, a fourth lens unithaving a negative refractive power, and a fifth lens unit having apositive refractive power, and the fourth lens unit is a focusing lensunit, and at the time of zooming from a wide angle end to a telephotoend, only the second lens unit and the fourth lens unit move, and thefirst lens unit, the third lens unit, and the fifth lens unit are fixed,and the following conditional expression (13) is satisfied:

|(y _(w7d′) −y _(w7d))/P|/(1/N)<250  (13)

where,

a side of the mount portion is let to be an object side and a side ofthe image pickup element is let to be an image side,

each of y_(w7d) and y_(w7d)′ is a height of a predetermined light ray ata position at which the predetermined light ray intersects an imageplane, and y_(w7d) denotes a light-ray height when focused to the firstobject and y_(w7d)′ denotes a light-ray height in a defocused state,here

the defocused state is a state in which the focusing lens unit is movedby Δ_(s2) when focused to the first object, and Δ_(s2)=10×P

0.0008<P<0.005,0.05<1/N<1,

where,

N denotes the number of pixels (unit millions of pixels) of the imagepickup element,

P denotes a pixel pitch (unit mm) of the image pickup element,

the predetermined light ray is a light ray with an angle of view of 7degrees at the wide angle end, which passes through a center of a lenssurface nearest to object of the zoom lens, and

the first object is an object when an object-point distance is 1000 mm,here

the object-point distance is a distance from a lens surface positionednearest to object of the zoom lens, up to the object.

The zoom lens used for the zoom image pickup apparatus according to thepresent embodiment can be used as an image pickup optical system forendoscope. When an image pickup optical system for endoscope is combinedwith an endoscope optical system, an entrance-pupil position isrestricted. Generally, an image pickup optical system for endoscope doesnot have an aperture stop. Therefore, an aperture of an image-forminglight beam is determined by an exit-pupil diameter. An eye-point of anendoscope optical system is a position where generally, there is noproblem for visual observation, such as a position few mm away from aneyepiece end surface.

Since the first lens unit is near the exit-pupil position of theendoscope optical system, an outer diameter becomes small. However,since the first lens unit affects the spherical aberrationsubstantially, it is not preferable for focusing. Therefore, by lettingthe fourth lens unit to be the focusing lens unit, a position of thefocusing lens unit becomes away from the exit-pupil position. Moreover,since the refractive power of the third lens unit is a positiverefractive power, it is possible to suppress a height of a light ray atthe focusing lens unit to be low. As a result of this, it is possible tosuppress the fluctuation in the spherical aberration at the time offocusing.

Furthermore, since the refractive power of the focusing lens unit is anegative refractive power, it is possible to make the focusingsensitivity high. As a result of this, it is possible to suppress anincrease in the amount of movement of the focusing lens unit at the timeof focusing.

Moreover, the fifth lens unit having a positive refractive power isdisposed on the image side of the focusing lens unit (fourth lens unit).In this case, the lens unit having a positive refractive power isdisposed next to a lens unit (focusing lens unit) having a negativerefractive power. Therefore, it is possible to suppress a fluctuation inan angle of view at the time of focusing.

Moreover, since a substantial zooming effect emanates by the second lensunit and the third lens unit, the second lens unit and the third lensunit become the main variator. Here, when the focusing lens unit ispositioned on the object side of the main variator, an amount ofvariation in the image height and an amount of variation in the imageposition due to the movement of the focusing lens unit variessubstantially according to the movement of the main variator. In suchmanner, the variation in the image height and the variation in the imageposition due to the movement of the focusing lens unit are affectedsubstantially by the movement of the main variator.

For this reason, by letting the fourth lens unit to be the focusing lensunit, the focusing lens unit is disposed next to the main variator.Therefore, since an effect of the main variator can be ignored, thefocusing sensitivity ceases to vary substantially. Moreover, since thevariation in the focusing sensitivity is small, it becomes easy tocontrol the movement of the focusing lens unit.

Conditional expression (13) is a conditional expression related to anamount of variation. y_(w7d) and y_(w7d)′ in conditional expression (13)will be described by using FIG. 1A and FIG. 1B. FIG. 1A shows an overallzoom lens and FIG. 1B is an enlarged view showing proximity of an imageplane. Moreover, L_(w7) shows a predetermined light ray, LA shows a lensnearest to object of the zoom lens, and Fo indicates the focusing lensunit.

FIG. 1A and FIG. 1B are diagrams showing how the image height variesaccording to a movement of the focusing lens unit Fo. In FIG. 1A andFIG. 1B, P1 is a position of the focusing lens unit Fo when focused to afirst object. Moreover, P2 is a position to which the focusing lens unitFo is moved only by a minute amount ΔS. For making the movement of thefocusing lens unit Fo easily understandable, the movement of thefocusing lens unit Fo is exaggeratedly illustrated in FIG. 1B.

The predetermined light ray L_(w7) is a light ray with an angle of viewof 7 degrees at the wide angle end. The predetermined light ray L_(w7)passes through a center of a lens surface on the object side of the lensLA.

In a state of a position of the focusing lens unit Fo coinciding withP1, a light ray incident on the focusing lens unit Fo advances as shownby a solid line, and reaches an image position. The image height at thistime becomes y_(w7d). From this state, the focusing lens unit Fo is letto undergo a wobbling operation. Accordingly, the focusing lens unit Fomoves to a position of P2.

In a state of the position of the focusing lens unit Fo coinciding withP2, a light ray incident on the focusing lens unit Fo advances as shownby a broken line, and reaches an image position. The image height atthis time becomes y_(w7d′). As shown in FIG. 1B, for the light ray ofthe angle of view of 7 degrees at the wide angle end, the image heightfluctuates between y_(w7d) and y_(w7d′) according to the position of thefocusing lens unit Fo.

In autofocusing, a focused state is maintained all the time by lettingthe focusing lens unit Fo undergo the wobbling operation. Therefore, inautofocusing, the amount of variation of the image height is sought tobe small at the time of movement of the focusing lens unit Fo.

Conditional expression (13) indicates as to how much the variation inthe image height is prominent on the image pickup element when thefocusing lens unit has fluctuated minutely. Since the amount ofvariation in the image height is divided by the pixel pitch, finer thepixel pitch, more prominent is the variation in the image height.Moreover, when a sensor size is same, larger the total number of pixels,finer is the pixel pitch. Therefore, conditional expression (13)reflects the fact that larger the number of pixels, more prominent isthe variation in the image height.

By satisfying conditional expression (13), it is possible to suppress anincrease in the amount of variation of the image height (y direction) atthe time of focusing. Accordingly, even at the time of observing anendoscope image on a television monitor upon enlarging for example, itis possible to use the endoscope without an uncomfortable feeling.

It is preferable that the following conditional expression (13′) besatisfied instead of conditional expression (13).

|(y _(w7d′) −y _(w7d))/P|/(1/N)<200  (13′)

Furthermore, it is more preferable that the following conditionalexpression (13″) be satisfied instead of conditional expression (13).

|(y _(w7d′) −y _(w7d))/P|/(1/N)<150  (13″)

Examples of zoom lenses to be used in the zoom image pickup apparatusaccording to the present invention will be described below in detail byreferring to the accompanying diagrams. However, the present inventionis not restricted to the examples described below. Moreover, as towhether the refractive power is positive or negative depends on aparaxial radius of curvature.

Moreover, a zoom lens in each of the following examples is to beconnected to an eyepiece portion. Generally, since an aperture stop isdisposed on an optical system of an optical instrument side, theaperture stop is not to be provided to the zoom lens side. However, fordesigning a zoom lens, an aperture stop is necessary. A virtual stop inthe following description of examples is an aperture stop provided fordesigning. Therefore, in the actual zoom lens, the aperture stop doesnot exist physically. However, sometimes a stop (such as a flareaperture) for shielding unnecessary light rays is disposed at a positionof the virtual stop.

Moreover, a position of a first object is a position when anobject-point distance is 1000 mm. Furthermore, a position of a secondobject is a position when the object-point distance is 333.33 mm, and atthe position of the second object, object is nearest to the zoom lens.

Cross-sectional views of each example will be described below.Cross-sectional views are lens cross-sectional views along an opticalaxis showing an optical arrangement when focused to the first object. Inthe cross-sectional views, F indicates a filter, CG indicates a coverglass, and I indicates an image pickup surface (image plane) of an imagepickup element. For instance, in a case of a type using three imagepickup elements (three-plate type), CG indicates a color separationprism and not a cover glass.

FIG. 2A, FIG. 4A, FIG. 6A, FIG. 8A, FIG. 10A, FIG. 12A, FIG. 14A, FIG.16A, and FIG. 18A show cross-sectional views at a wide angle end;

FIG. 2B, FIG. 4B, FIG. 6B, FIG. 8B, FIG. 10B, FIG. 12B, FIG. 14B, FIG.16B, and FIG. 18B show cross-sectional views in an intermediate focallength state.

FIG. 2C, FIG. 4C, FIG. 6C, FIG. 8C, FIG. 10C, FIG. 12C, FIG. 14C, FIG.16C, and FIG. 18C show cross-sectional views at a telephoto end.

Aberration diagrams for each example will be described below. Aberrationdiagrams are aberration diagrams at the time of focusing to a firstobject.

FIG. 3A, FIG. 5A, FIG. 7A, FIG. 9A, FIG. 11A, FIG. 13A, FIG. 15A, FIG.17A, and FIG. 19A show a spherical aberration (SA) at the wide angleend.

FIG. 3B, FIG. 5B, FIG. 7B, FIG. 9B, FIG. 11B, FIG. 13B, FIG. 15B, FIG.17B, and FIG. 19B show an astigmatism (AS) at the wide angle end.

FIG. 3C, FIG. 5C, FIG. 7C, FIG. 9C, FIG. 11C, FIG. 13C, FIG. 15C, FIG.170, and FIG. 19C show a distortion (DT) at the wide angle end.

FIG. 3D, FIG. 5D, FIG. 7D, FIG. 9D, FIG. 11D, FIG. 13D, FIG. 15D, FIG.17D, and FIG. 19D show a chromatic aberration of magnification (CC) atthe wide angle end.

FIG. 3E, FIG. 5E, FIG. 7E, FIG. 9E, FIG. 11E, FIG. 13E, FIG. 15E, FIG.17E, and FIG. 19E show a spherical aberration (SA) in the intermediatefocal length state.

FIG. 3F, FIG. 5F, FIG. 7F, FIG. 9F, FIG. 11F, FIG. 13F, FIG. 15F, FIG.17F, and FIG. 19F show an astigmatism (AS) in the intermediate focallength state.

FIG. 3G, FIG. 5G, FIG. 7G, FIG. 9G, FIG. 11G, FIG. 13G, FIG. 15G, FIG.17G, and FIG. 19G show a distortion (DT) in the intermediate focallength state.

FIG. 3H, FIG. 5H, FIG. 7H, FIG. 9H, FIG. 11H, FIG. 13H, FIG. 15H, FIG.17H, and FIG. 19H show a chromatic aberration of magnification (CC) inthe intermediate focal length state.

FIG. 3I, FIG. 5I, FIG. 7I, FIG. 9I, FIG. 11I, FIG. 13I, FIG. 15I, FIG.17I, and FIG. 19I show a spherical aberration (SA) at the telephoto end.

FIG. 3J, FIG. 5J, FIG. 7J, FIG. 9J, FIG. 11J, FIG. 13J, FIG. 15J, FIG.17J, and FIG. 19J show an astigmatism (AS) at the telephoto end.

FIG. 3K, FIG. 5K, FIG. 7K, FIG. 9K, FIG. 11K, FIG. 13K, FIG. 15K, FIG.17K, and FIG. 19K show a distortion (DT) at the telephoto end.

FIG. 3L, FIG. 5L, FIG. 7L, FIG. 9L, FIG. 11L, FIG. 13L, FIG. 15L, FIG.17L, and FIG. 19L show a chromatic aberration of magnification (CC) atthe telephoto end.

A zoom lens according to an example 1 will be described below.

A zoom lens according to the example 1 includes in order from an objectside, a first lens unit G1 having a positive refractive power, a secondlens unit G2 having a negative refractive power, a third lens unit G3having a positive refractive power, a fourth lens unit G4 having anegative refractive power, and a fifth lens unit G5 having a positiverefractive power.

The first lens unit G1 includes a negative meniscus lens L1 having aconvex surface directed toward an image side, a biconvex positive lensL2, and a negative meniscus lens L3 having a convex surface directedtoward the image side. Here, the biconvex positive lens L2 and thenegative meniscus lens L3 are cemented. A virtual stop is set to bepositioned on an image-side surface of the negative meniscus lens L3.

The second lens unit G2 includes a positive meniscus lens L4 having aconvex surface directed toward the image side and a biconcave negativelens L5. Here, the positive meniscus lens L4 and the biconcave negativelens L5 are cemented.

The third lens unit G3 includes a biconvex positive lens L6, a biconvexpositive lens L7, and a biconcave negative lens L8. Here, the biconvexpositive lens L7 and the biconcave negative lens L8 are cemented.

The fourth lens unit G4 includes a biconcave negative lens L9.

The fifth lens unit G5 includes a biconvex positive lens L10 and anegative meniscus lens L11 having a convex surface directed toward theimage side. Here, the biconvex positive lens L10 and the negativemeniscus lens L11 are cemented.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 is fixed, the second lens unit G2 moves toward theimage side, the third lens unit G3 is fixed, the fourth lens unit G4moves toward the image side, and fifth lens unit G5 is fixed.

Moreover, focusing to an object is carried out by a movement of thefourth lens unit G4. At the time of focusing from a first object to asecond object, the biconcave negative lens L9 moves toward the imageside.

Next, a zoom lens according to an example 2 will be described below.

The zoom lens according to the example 2 includes in order from anobject side, a first lens unit G1 having a positive refractive power, asecond lens unit G2 having a negative refractive power, a third lensunit G3 having a positive refractive power, a fourth lens unit G4 havinga negative refractive power, and a fifth lens unit G5 having a positiverefractive power.

The first lens unit G1 includes a negative meniscus lens L1 having aconvex surface directed toward an image side, a biconvex positive lensL2, and a biconcave negative lens L3. Here, the biconvex positive lensL2 and the biconcave negative lens L3 are cemented. A virtual stop isset to be positioned on an image-side surface of the biconcave negativelens L3.

The second lens unit G2 includes a biconcave negative lens L4 and apositive meniscus lens L5 having a convex surface directed toward theobject side. Here, the biconcave negative lens L4 and the positivemeniscus lens L5 are cemented.

The third lens unit G3 includes a positive meniscus lens L6 having aconvex surface directed toward the image side, a biconvex positive lensL7, a negative meniscus lens L8 having a convex surface directed towardthe image side, a negative meniscus lens L9 having a convex surfacedirected toward the object side, and a positive meniscus lens L10 havinga convex surface directed toward the object side. Here, the biconvexpositive lens L7 and the negative meniscus lens L8 are cemented.Moreover, the negative meniscus lens L9 and the positive meniscus lensL10 are cemented.

The fourth lens unit G4 includes a negative meniscus lens L11 having aconvex surface directed toward the image side and a biconcave negativelens L12. Here, the negative meniscus lens L11 and the biconcavenegative lens L12 are cemented.

The fifth lens unit G5 includes a biconvex positive lens L13 and abiconcave negative lens L14.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 is fixed, the second lens unit G2 moves toward theimage side, the third lens unit G3 is fixed, the fourth lens unit G4moves toward the image side, and the fifth lens unit G5 is fixed.

Moreover, focusing to an object is carried out by a movement of thefourth lens unit G4. At the time of focusing from a first object to asecond object, the negative meniscus lens L11 and the biconcave negativelens L12 move toward the image side.

Next, a zoom lens according to an example 3 will be described below.

The zoom lens according to the example 3 includes in order from anobject side, a first lens unit G1 having a positive refractive power, asecond lens unit G2 having a negative refractive power, a third lensunit G3 having a positive refractive power, a fourth lens unit G4 havinga negative refractive power, and a fifth lens unit G5 having a positiverefractive power.

The first lens unit G1 includes a negative meniscus lens L1 having aconvex surface directed toward the object side, a biconvex positive lensL2, and a biconcave negative lens L3. Here, the biconvex positive lensL2 and the biconcave negative lens L3 are cemented. A virtual stop isset to be positioned on an image-side surface of the biconcave negativelens L3.

The second lens unit G2 includes a biconcave negative lens L4 and apositive meniscus lens L5 having a convex surface directed toward theobject side. Here, the biconcave negative lens L4 and the positivemeniscus lens L5 are cemented.

The third lens unit G3 includes a biconvex positive lens L6, a biconvexpositive lens L7, a biconcave negative lens L8, a negative meniscus lensL9 having a convex surface directed toward the object side, and abiconvex positive lens L10. Here, the biconvex positive lens L7 and thebiconcave negative lens L8 are cemented. Moreover, the negative meniscuslens L9 and the biconvex positive lens L10 are cemented.

The fourth lens unit G4 includes a biconcave negative lens L11.

The fifth lens unit G5 includes a biconvex positive lens L12, a biconvexpositive lens L13, a negative meniscus lens L14 having a convex surfacedirected toward an image side, a positive meniscus lens L15 having aconvex surface directed toward the image side, and a biconcave negativelens L16. Here, the biconvex positive lens L13 and the negative meniscuslens L14 are cemented.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 is fixed, the second lens unit G2 moves toward theimage side, the third lens unit G3 is fixed, the fourth lens unit G4moves toward the image side, and the fifth lens unit G5 is fixed. Aposition of the fourth lens unit G4 is same in an intermediate focallength state and at the telephoto end.

Moreover, focusing to an object is carried out by a movement of thefourth lens unit G4. At the time of focusing from a first object to asecond object, the biconcave negative lens L11 moves toward the imageside.

Next, a zoom lens according to an example 4 will be described below.

The zoom lens according to the example 4 includes in order from anobject side, a first lens unit G1 having a positive refractive power, asecond lens unit G2 having a negative refractive power, a third lensunit G3 having a positive refractive power, a fourth lens unit G4 havinga negative refractive power, and a fifth lens unit G5 having a positiverefractive power.

The first lens unit G1 includes a biconvex positive lens L1 and abiconcave negative lens L2. Here, the biconvex positive lens L1 and thebiconcave negative lens L2 are cemented. A virtual stop is set to bepositioned on an image-side surface of the biconcave negative lens L2.

The second lens unit G2 includes a biconcave negative lens L3 and apositive meniscus lens L4 having a convex surface directed toward theobject side. Here, the biconcave negative lens L3 and the positivemeniscus lens L4 are cemented.

The third lens unit G3 includes a biconvex positive lens L5, a negativemeniscus lens L6 having a convex surface directed toward the objectside, and a biconvex positive lens L7. Here, the negative meniscus lensL6 and the biconvex positive lens L7 are cemented.

The fourth lens unit G4 includes a negative meniscus lens L8 having aconvex surface directed toward the object side.

The fifth lens unit G5 includes a biconvex positive lens L9, a biconvexpositive lens L10, and a biconcave negative lens L11. Here, the biconvexpositive lens L10 and the biconcave negative lens L11 are cemented.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 is fixed, the second lens unit G2 moves toward animage side, the third lens unit G3 is fixed, the fourth lens unit G4moves toward the image side, and the fifth lens unit G5 is fixed.

Moreover, focusing to an object is carried out by a movement of thefourth lens unit G4. At the time of focusing from a first object to asecond object, the negative meniscus lens L8 moves toward the imageside.

An aspheric surface is provided to two surfaces namely, both surfaces ofthe biconvex positive lens L5.

Next, a zoom lens according to an example 5 will be described below.

The zoom lens according to the example 5 includes in order from anobject side, a first lens unit G1 having a positive refractive power, asecond lens unit G2 having a negative refractive power, a third lensunit G3 having a positive refractive power, a fourth lens unit G4 havinga negative refractive power, and a fifth lens unit G5 having a positiverefractive power.

The first lens unit G1 includes a negative meniscus lens L1 having aconvex surface directed toward an image side, a biconvex positive lensL2, and a negative meniscus lens L3 having a convex surface directedtoward the image side. Here, the biconvex positive lens L2 and thenegative meniscus lens L3 are cemented. A virtual stop is set to bepositioned on an image-side surface of the negative meniscus lens L3.

The second lens unit G2 includes a biconcave negative lens L4 and apositive meniscus lens L5 having a convex surface directed toward theobject side. Here, the biconcave negative lens L4 and the positivemeniscus lens L5 are cemented.

The third lens unit G3 includes a positive meniscus lens L6 having aconvex surface directed toward the image side, a biconvex positive lensL7, a negative meniscus lens L8 having a convex surface directed towardthe image side, a negative meniscus lens L9 having a convex surfacedirected toward the object side, and a biconvex positive lens L10. Here,the biconvex positive lens L7 and the negative meniscus lens L8 arecemented. Moreover, the negative meniscus lens L9 and the biconvexpositive lens L10 are cemented.

The fourth lens unit G4 includes a negative meniscus lens L11 having aconvex surface directed toward the image side and a biconcave negativelens L12.

The fifth lens unit G5 includes a biconvex positive lens L13 and anegative meniscus lens L14 having a convex surface directed toward theimage side.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 is fixed, the second lens unit G2 moves toward theimage side, the third lens unit G3 is fixed, the fourth lens unit G4moves toward the image side, and the fifth lens unit G5 is fixed.

Moreover, focusing to an object is carried out by a movement of thefourth lens unit G4. At the time of focusing from a first object to asecond object, the negative meniscus lens L11 and the biconcave negativelens L12 move toward the image side.

Next, a zoom lens according to an example 6 will be described below.

The zoom lens according to the example 6 includes in order from anobject side, a first lens unit G1 having a positive refractive power, asecond lens unit G2 having a negative refractive power, a third lensunit G3 having a positive refractive power, a fourth lens unit G4 havinga negative refractive power, and a fifth lens unit G5 having a positiverefractive power.

The first lens unit G1 includes a negative meniscus lens L1 having aconvex surface directed toward the object side, a biconvex positive lensL2, and a biconcave negative lens L3. Here, the biconvex positive lensL2 and the biconcave negative lens L3 are cemented. A virtual stop isset to be positioned on an image-side surface of the biconcave negativelens L3.

The second lens unit G2 includes a biconcave negative lens L4 and apositive meniscus lens L5 having a convex surface directed toward theobject side. Here, the biconcave negative lens L4 and the positivemeniscus lens L5 are cemented.

The third lens unit G3 includes a biconvex positive lens L6, a biconvexpositive lens L7, a negative meniscus lens L8 having a convex surfacedirected toward an image side, a negative meniscus lens L9 having aconvex surface directed toward the object side, and a positive meniscuslens L10 having a convex surface directed toward the object side. Here,the biconvex positive lens L7 and the negative meniscus lens L8 arecemented. Moreover, the negative meniscus lens L9 and the positivemeniscus lens L10 are cemented.

The fourth lens unit G4 includes a biconcave negative lens L11.

The fifth lens unit G5 includes a biconvex positive lens L12, a biconvexpositive lens L13, a negative meniscus lens L14 having a convex surfacedirected toward the image side, a negative meniscus lens L15 having aconvex surface directed toward the image side, and a negative meniscuslens L16 having a convex surface directed toward the object side.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 is fixed, the second lens unit G2 moves toward theimage side, the third lens unit G3 is fixed, the fourth lens unit G4moves toward the image side, and the fifth lens unit G5 is fixed.

Moreover, focusing to an object is carried out by a movement of thefourth lens unit G4. At the time of focusing from a first object to asecond object, the biconcave negative lens L11 moves toward the imageside.

Next, a zoom lens according to an example 7 will be described below.

The zoom lens according to the example 7 includes in order from anobject side, a first lens unit G1 having a positive refractive power, asecond lens unit G2 having a negative refractive power, a third lensunit G3 having a positive refractive power, a fourth lens unit G4 havinga negative refractive power, and a fifth lens unit G5 having a positiverefractive power.

The first lens unit G1 includes a negative meniscus lens L1 having aconvex surface directed toward an image side, a biconvex positive lensL2, and a negative meniscus lens L3 having a convex surface directedtoward the image side. Here, the biconvex positive lens L2 and thenegative meniscus lens L3 are cemented. A virtual stop is set to bepositioned on an image-side surface of the negative meniscus lens L3.

The second lens unit G2 includes a positive meniscus lens L4 having aconvex surface directed toward the image side and a biconcave negativelens L5. Here, the positive meniscus lens L4 and the biconcave negativelens L5 are cemented.

The third lens unit G3 includes a biconvex positive lens L6, a biconvexpositive lens L7, and a biconcave negative lens L8. Here, the biconvexpositive lens L7 and the biconcave negative lens L8 are cemented.

The fourth lens unit G4 includes a biconcave negative lens L9.

The fifth lens unit G5 includes a biconvex positive lens L10 and anegative meniscus lens L11 having a convex surface directed toward theimage side. Here, the biconvex positive lens L10 and the negativemeniscus lens L11 are cemented.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 is fixed, the second lens unit G2 moves toward theimage side, the third lens unit G3 is fixed, the fourth lens unit G4moves toward the image side, and the fifth lens unit G5 is fixed.

Moreover, focusing to an object is carried out by a movement of thefourth lens unit G4. At the time of focusing from a first object to asecond object, the biconcave negative lens L9 moves toward the imageside.

Next, a zoom lens according to an example 8 will be described below.

The zoom lens according to the example 8 includes in order from anobject side, a first lens unit G1 having a positive refractive power, asecond lens unit G2 having a negative refractive power, a third lensunit G3 having a positive refractive power, a fourth lens unit G4 havinga negative refractive power, and a fifth lens unit G5 having a positiverefractive power.

The first lens unit G1 includes a negative meniscus lens L1 having aconvex surface directed toward the object side, a biconvex positive lensL2, and a biconcave negative lens L3. Here, the biconvex positive lensL2 and the biconcave negative lens L3 are cemented. A virtual stop isset to be positioned on an image-side surface of the biconcave negativelens L3.

The second lens unit G2 includes a biconcave negative lens L4 and apositive meniscus lens L5 having a convex surface directed toward theobject side. Here, the biconcave negative lens L4 and the positivemeniscus lens L5 are cemented.

The third lens unit G3 includes a biconvex positive lens L6, a biconvexpositive lens L7, a negative meniscus lens L8 having a convex surfacedirected toward an image side, a negative meniscus lens L9 having aconvex surface directed toward the object side, and a biconvex positivelens L10. Here, the biconvex positive lens L7 and the negative meniscuslens L8 are cemented. Moreover, the negative meniscus lens L9 and thebiconvex positive lens L10 are cemented.

The fourth lens unit G4 includes a biconcave negative lens L11.

The fifth lens unit G5 includes a biconvex positive lens L12, a biconvexpositive lens L13, a negative meniscus lens L14 having a convex surfacedirected toward the image side, a positive meniscus lens L15 having aconvex surface directed toward the image side, and a biconcave negativelens L16.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 is fixed, the second lens unit G2 moves toward theimage side, the third lens unit G3 is fixed, the fourth lens unit G4moves toward the image side, and the fifth lens unit G5 is fixed.

Moreover, focusing to an object is carried out by a movement of thefourth lens unit G4. At the time of focusing forma first object to asecond object, the biconcave negative lens L11 moves toward the imageside.

Next, a zoom lens according to an example 9 will be described below.

The zoom lens according to the example 9 includes in order from anobject side, a first lens unit G1 having a positive refractive power, asecond lens unit G2 having a negative refractive power, a third lensunit G3 having a positive refractive power, a fourth lens unit G4 havinga negative refractive power, and a fifth lens unit G5 having a positiverefractive power.

The first lens unit G1 includes a negative meniscus lens L1 having aconvex surface directed toward the object side, a positive meniscus lensL2 having a convex surface directed toward the object side, and abiconvex positive lens L3. Here, the positive meniscus lens L2 and thebiconvex positive lens L3 are cemented. A virtual stop is set to bepositioned on an image-side surface of the biconvex positive lens L3.

The second lens unit G2 includes a biconcave negative lens L4 and apositive meniscus lens L5 having a convex surface directed toward theobject side. Here, the biconcave negative lens L4 and the positivemeniscus lens L5 are cemented.

The third lens unit G3 includes a biconvex positive lens L6, a biconvexpositive lens L7, a biconcave negative lens L8, a negative meniscus lensL9 having a convex surface directed toward the object side, and apositive meniscus lens L10 having a convex surface directed toward theobject side. Here, the biconvex positive lens L7 and the biconcavenegative lens L8 are cemented. Moreover, the negative meniscus lens L9and the positive meniscus lens L10 are cemented.

The fourth lens unit G4 includes a biconcave negative lens L11.

The fifth lens unit G5 includes a biconvex positive lens L12, a negativemeniscus lens L13 having a convex surface directed toward an image side,and a negative meniscus lens L14 having a convex surface directed towardthe image side. Here, the biconvex positive lens L12 and the negativemeniscus lens L13 are cemented.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 is fixed, the second lens unit G2 moves toward theimage side, the third lens unit G3 moves toward the object side, thefourth lens unit G4 is fixed, and the fixed lens unit G5 is fixed.

Moreover, focusing to an object is carried out by a movement of thefourth lens unit G4. At the time of focusing from a first object to asecond object, the biconcave negative lens L11 moves toward the imageside.

Next, numerical data of optical components comprising the zoom lens ofeach above example are shown. In numerical data of each example, r1, r2,. . . denotes a curvature radius of each lens surface, d1, d2, . . .denotes a thickness of each lens or an air distance between adjacentlens surfaces, nd1, nd2, . . . denotes a refractive index of each lensfor d-line, v1, vd2, . . . denotes an Abbe number of each lens, ERdenotes an effective diameter, * denotes an aspheric surface. Moreover,in zoom data, f denotes a focal length of an overall zoom lens system,FNO. denotes F-number, FE denotes a back focus, IH denotes an imageheight, ω denotes a half angle of field, f1, f2 . . . is a focal lengthof each lens unit. Further, Lens total length is the distance from thefrontmost lens surface to the rearmost lens surface plus the back focus.The back focus is a unit which is expressed upon air conversion of adistance from the lens backmost surface to a paraxial image surface.

Moreover, WE1, ST1 and TE1 denote a wide angle end, an intermediatestate and a telephoto end, respectively, at a state of focusing to thefirst object. WE2, ST2 and TE2 denote a wide angle end, an intermediatestate and a telephoto end, respectively, at a state of focusing to thesecond object. Further, a value of IH and a value of w do not denote avalue at focal length in each state.

Moreover, a shape of an aspheric surface is defined by the followingexpression where the direction of the optical axis is represented by z,the direction orthogonal to the optical axis is represented by y, aconical coefficient is represented by K, aspheric surface coefficientsare represented by A4, A6, A8, A10

Z=(y ² /r)/[1+{1−(1+k)(y/r)²}^(1/2) ]+A4y ⁴ +A6y ⁶ +A8y ⁸ +A10y ¹⁰

Further, in the aspherical surface coefficients, ‘e−n’ (where, n is anintegral number) indicates ‘10^(−n)’. Moreover, these symbols arecommonly used in the following numerical data for each example.

Example 1

Unit mm Surface data Surface no. r d nd νd ER Object plane ∞ ∞  1−12.214 2.70 1.58144 40.75 2.1728  2 −20.622 0.30 2.1487  3 38.082 1.801.48749 70.23 2.1132  4 −8.106 0.70 1.78590 44.20 2.0107  5 −12.145Variable  6 −15.671 1.42 1.92286 18.90 2.0982  7 −7.610 0.70 1.7495135.33 2.2171  8 25.752 Variable 2.3026  9 258.336 1.75 1.75500 52.324.802 10 −19.896 0.30 4.9185 11 15.793 3.00 1.72916 54.68 4.9117 12−20.119 1.20 1.80518 25.42 4.6805 13 130.235 Variable 4.4587 14 −32.6750.70 1.72916 54.68 3.83 15 18.164 Variable 3.7522 16 28.066 3.00 1.8830040.76 3.9661 17 −10.669 0.70 1.78472 25.68 3.8877 18 −151.242 Variable3.8001 19 ∞ 1.00 1.52113 66.54 20 ∞ 0.50 21 ∞ 14.90  1.51633 64.14 22 ∞0.70 Image plane ∞ Zoom data Zoom ratio 1.97 WE1 ST1 TE1 WE2 ST2 TE2 f15.83 21.69 31.22 15.74 21.41 30.24 FNO. 4.41 6.04 8.69 4.38 5.96 8.42FB 19.44 19.44 19.44 19.44 19.44 19.44 LTL 59.28 59.28 59.28 59.28 59.2859.28 d5 1.60 6.49 12.20 1.60 6.49 12.20 d8 12.23 7.34 1.62 12.23 7.341.62 d13 3.55 4.17 4.22 3.82 4.70 5.36 d15 4.20 3.57 3.52 3.92 3.04 2.38d18 2.34 2.34 2.34 2.34 2.34 2.34 IH 1.92 2.73 3.00 1.92 2.73 3.00 ω7.03 7.28 5.46 7.1 7.36 5.46 Unit focal length f1 = 35.30 f2 = −15.16 f3= 12.75 f4 = −15.85 f5 = 22.17

Example 2

Unit mm Surface data Surface no. r d nd νd ER Object plane ∞ ∞  1−15.012 0.70 1.88300 40.76 3.5678  2 −16.475 0.50 3.6075  3 52.044 1.701.80610 40.92 3.5081  4 −16.001 0.70 1.72151 29.23 3.4058  5 4134.942Variable  6 −35.115 0.70 1.80610 40.92 3.3334  7 10.106 1.87 1.8466623.78 3.4484  8 35.596 Variable 3.5458  9 −1832.152 2.27 1.80610 40.927.4671 10 −28.959 0.50 7.6195 11 58.441 4.00 1.57135 52.95 7.6161 12−15.741 0.70 1.74077 27.79 7.5389 13 −87.401 0.78 7.5633 14 12.676 0.801.69895 30.13 7.4011 15 9.422 4.41 1.49700 81.61 6.9479 16 199.193Variable 6.6287 17 −50.492 2.15 1.92286 18.90 5.9176 18 −29.717 0.701.58144 40.75 5.7288 19 9.709 Variable 5.2644 20 14.909 4.00 1.7291654.68 5.7444 21 −24.171 5.94 5.4936 22 −22.094 0.70 1.80518 25.42 2.863523 68.660 Variable 2.7234 24 ∞ 1.00 1.52113 66.54 25 ∞ 0.50 26 ∞ 0.701.51633 64.14 27 ∞ 0.50 Image plane ∞ Zoom data Zoom ratio 1.97 WE1 ST1TE1 WE2 ST2 TE2 f 16.30 22.01 32.14 16.10 21.43 29.95 FNO. 2.49 3.364.91 2.46 3.27 4.58 FB 4 4 4 4 4 4 LTL 63.50 63.50 63.50 63.50 63.5063.50 d5 0.68 8.00 17.19 0.68 8.00 17.19 d8 18.22 10.89 1.71 18.22 10.891.71 d16 2.70 3.33 3.70 3.09 4.06 5.35 d19 4.78 4.15 3.78 4.39 3.43 2.13d23 1.30 1.30 1.30 1.30 1.30 1.30 IH 1.92 2.73 3.00 1.92 2.73 3.00 ω6.83 7.17 5.25 6.95 7.35 5.33 Unit focal length f1 = 58.87 f2 = −23.06f3 = 15.86 f4 = −14.67 f5 = 18.15

Example 3

Unit mm Surface data Surface no. r d nd νd ER Object plane ∞ ∞  1 50.1950.70 1.57135 52.95 3.8202  2 14.605 1.84 3.7125  3 16.895 3.10 1.8040046.57 3.6868  4 −28.288 0.70 1.69895 30.13 3.4197  5 69.580 Variable  6−41.811 0.70 1.88300 40.76 3.3333  7 13.843 1.76 1.84666 23.78 3.4287  858.330 Variable 3.5461  9 82.739 2.52 1.88300 40.76 7.6069 10 −34.2830.30 7.6897 11 32.941 3.78 1.69680 55.53 7.517 12 −19.967 0.70 2.0033028.27 7.2943 13 385.813 0.30 7.1693 14 13.921 0.70 1.72825 28.46 6.962415 10.726 3.77 1.48749 70.23 6.6331 16 −412.981 Variable 6.3211 17−210.166 0.70 1.58913 61.14 5.2422 18 8.832 Variable 4.8053 19 14.7583.40 1.49700 81.61 5.1012 20 −20.808 0.30 4.9371 21 27.266 3.59 1.8830040.76 4.5942 22 −10.640 0.70 1.72916 54.68 4.0655 23 −38.106 0.48 3.680224 −20.137 1.00 1.72825 28.46 3.435 25 −16.275 0.32 3.1938 26 −14.3581.00 1.72825 28.46 2.9512 27 11.916 Variable 2.5692 28 ∞ 1.00 1.5211366.54 29 ∞ 0.50 30 ∞ 0.70 1.51633 64.14 31 ∞ 0.50 Image plane ∞ Zoomdata Zoom ratio 1.97 WE1 ST1 TE1 WE2 ST2 TE2 f 15.79 21.32 31.14 15.5620.69 28.96 FNO. 2.39 3.23 4.72 2.36 3.14 4.39 FB 3.44 3.44 3.44 3.443.44 3.44 LTL 65.00 65.00 65.00 65.00 65.00 65.00 d5 0.68 8.84 19.150.68 8.84 19.15 d8 19.27 11.11 0.80 19.27 11.11 0.80 d16 3.13 3.53 3.533.49 4.20 5.03 d18 6.12 5.72 5.72 5.76 5.06 4.22 d27 0.74 0.74 0.74 0.740.74 0.74 IH 1.92 2.73 3.00 1.92 2.73 3.00 ω 7.04 7.41 5.45 7.21 7.655.59 Unit focal length f1 = 62.65 f2 = −25.80 f3 = 14.80 f4 = −14.31 f5= 19.10

Example 4

Unit mm Surface data Surface no. r d nd νd ER Object plane ∞ ∞  1 30.6622.72 1.80400 46.57 3.6956  2 −22.684 0.70 1.80100 34.97 3.4261  3 64.717Variable  4 −38.528 0.70 1.80610 40.92 3.3288  5 11.707 1.87 1.8466623.78 3.4425  6 38.468 Variable 3.5547  7* 15.786 3.87 1.58913 61.148.3436  8* −78.080 0.30 8.1822  9 19.438 0.70 1.78472 25.68 7.9479 1010.466 5.71 1.48749 70.23 7.4128 11 −27.757 Variable 7.1991 12 34.2860.70 1.69680 55.53 5.679 13 9.038 Variable 5.1727 14 13.594 2.88 1.7725049.60 5.1601 15 −34.478 0.30 4.8934 16 12.804 3.59 1.51633 64.14 4.239617 −18.940 0.70 1.74951 35.33 3.1091 18 6.368 Variable 2.602 19 ∞ 1.001.52113 66.54 20 ∞ 0.50 21 ∞ 0.70 1.51633 64.14 22 ∞ 0.50 Image plane ∞Aspherical surface data 7th surface k = 0.000 A4 = −9.21106e−06, A6 =6.75309e−08, A8 = 1.55922e−09 8th surface k = 0.000 A4 = 7.46114e−05, A6= 1.19205e−07, A8 = 1.16426e−09 Zoom data Zoom ratio 1.97 WE1 ST1 TE1WE2 ST2 TE2 f 15.83 21.69 31.22 15.51 20.82 28.31 FNO. 2.28 3.13 4.502.24 3.00 4.08 FB 3.82 3.82 3.82 3.82 3.82 3.82 LTL 59.74 59.74 59.7459.74 59.74 59.74 d3 0.59 9.15 18.94 0.59 9.15 18.94 d6 19.22 10.66 0.8719.22 10.66 0.87 d11 2.91 3.60 4.09 3.32 4.40 5.94 d13 8.46 7.77 7.288.04 6.96 5.43 d18 1.12 1.12 1.12 1.12 1.12 1.12 IH 1.92 2.73 3.00 1.922.73 3.00 ω 7.03 7.28 5.38 7.22 7.57 5.58 Unit focal length f1 = 68.55f2 = −24.98 f3 = 14.86 f4 = −17.74 f5 = 26.57

Example 5

Unit mm Surface data Surface no. r d nd νd ER Object plane ∞ ∞  1−14.562 1.68 1.88300 40.76 3.2034  2 −17.237 0.50 3.2719  3 66.245 1.651.80610 40.92 3.185  4 −13.676 0.70 1.72151 29.23 3.093  5 −165.866Variable  6 −30.624 0.70 1.80610 40.92 3.0285  7 10.283 1.82 1.8466623.78 3.1446  8 37.753 Variable 3.257  9 −277.278 2.18 1.80610 40.927.1005 10 −27.086 0.50 7.2694 11 61.882 2.90 1.57135 52.95 7.3011 12−23.873 0.70 1.74077 27.79 7.2573 13 −76.315 0.50 7.2606 14 11.993 0.701.69895 30.13 7.0477 15 8.513 4.63 1.49700 81.61 6.5643 16 −547.927Variable 6.2284 17 −28.802 1.69 1.80518 25.42 5.4826 18 −42.509 0.305.3091 19 −37.850 0.70 1.58144 40.75 5.2329 20 10.790 Variable 4.9631 2117.656 4.00 1.72916 54.68 5.4951 22 −19.207 6.51 5.3212 23 −16.688 0.701.80518 25.42 2.6391 24 −158.795 Variable 2.5319 25 ∞ 1.00 1.52113 66.5426 ∞ 0.50 27 ∞ 0.70 1.51633 64.14 28 ∞ 0.50 Image plane ∞ Zoom data Zoomratio 1.97 WE1 ST1 TE1 WE2 ST2 TE2 f 15.00 20.25 29.58 14.84 19.80 27.89FNO. 2.62 3.54 5.17 2.60 3.46 4.88 FB 3.20 3.20 3.20 3.20 3.20 3.20 LTL61.85 61.85 61.85 61.85 61.85 61.85 d5 0.50 7.61 16.28 0.50 7.61 16.28d8 17.52 10.41 1.74 17.52 10.41 1.74 d16 2.60 3.25 3.91 2.86 3.73 5.01d20 4.98 4.33 3.67 4.72 3.85 2.57 d24 0.50 0.50 0.50 0.50 0.50 0.50 IH1.92 2.73 3.00 1.92 2.73 3.00 ω 7.43 7.81 5.72 7.55 7.99 5.82 Unit focallength f1 = 57.89 f2 = −21.98 f3 = 14.12 f4 = −12.37 f5 = 17.24

Example 6

Unit mm Surface data Surface no. r d nd νd ER Object plane ∞ ∞  1 68.8551.05 1.57135 52.95 3.895  2 15.829 1.91 3.759  3 18.450 3.84 1.8040046.57 3.7329  4 −29.377 0.70 1.69895 30.13 3.4079  5 98.570 Variable  6−42.649 0.70 1.88300 40.76 3.3369  7 14.728 1.67 1.84666 23.78 3.4329  857.254 Variable 3.548  9 88.682 2.53 1.88300 40.76 9.3055 10 −48.9660.30 9.3736 11 33.990 4.00 1.51633 64.14 9.224 12 −27.094 0.70 1.8051825.42 9.0672 13 −81.961 0.30 8.9749 14 13.885 0.74 1.78472 25.68 8.304415 10.591 4.08 1.49700 81.61 7.7434 16 67.637 Variable 7.394 17 −107.6730.70 1.67003 47.23 6.1122 18 10.162 Variable 5.5699 19 15.470 3.621.49700 81.61 5.9803 20 −19.677 1.62 5.8377 21 30.113 4.00 1.80610 40.924.9025 22 −6.601 0.70 1.77250 49.60 4.4299 23 −44.340 0.69 3.7974 24−13.842 1.00 1.72151 29.23 3.5295 25 −26.023 0.34 3.287 26 42.532 1.001.88300 40.76 2.9757 27 11.022 Variable 2.6451 28 ∞ 1.00 1.52113 66.5429 ∞ 0.50 30 ∞ 0.70 1.51633 64.14 31 ∞ 0.50 Image plane ∞ Zoom data Zoomratio 2.50 WE1 ST1 TE1 WE2 ST2 TE2 f 15.79 23.69 39.48 15.59 22.92 35.20FNO. 2.40 3.60 5.99 2.37 3.48 5.35 FB 3.47 3.47 3.47 3.47 3.47 3.47 LTL77.00 77.00 77.00 77.00 77.00 77.00 d5 0.67 12.17 26.50 0.67 12.17 26.50d8 26.64 15.13 0.80 26.64 15.13 0.80 d16 3.60 4.30 4.41 3.90 4.98 6.49d18 6.42 5.72 5.61 6.12 5.04 3.52 d27 0.77 0.77 0.77 0.77 0.77 0.77 IH1.92 2.73 3.00 1.92 2.73 3.00 ω 7.08 6.73 4.26 7.29 7.05 4.43 Unit focallength f1 = 68.65 f2 = −26.01 f3 = 15.88 f4 = −13.76 f5 = 19.45

Example 7

Unit mm Surface data Surface no. r d nd νd ER Object plane ∞ ∞  1−11.701 2.79 1.88300 40.76 2.0965  2 −15.802 0.30 2.156  3 42.274 1.711.49700 81.61 2.1142  4 −9.698 0.70 1.88300 40.76 2.01  5 −13.684Variable  6 −13.944 1.48 1.92286 18.90 2.0974  7 −6.064 0.70 1.8010034.97 2.2253  8 27.196 Variable 2.3294  9 34.781 2.30 1.78800 47.375.6313 10 −24.168 3.65 5.6898 11 14.811 3.00 1.72916 54.68 5.1501 12−15.411 1.20 1.92286 18.90 4.8761 13 229.642 Variable 4.5686 14 −19.2580.70 1.49700 81.61 4.1099 15 9.619 Variable 3.9054 16 82.597 3.001.69680 55.53 4.2179 17 −6.836 0.70 1.56883 56.36 4.2416 18 −33.232Variable 4.1506 19 ∞ 1.00 1.52113 66.54 20 ∞ 0.50 21 ∞ 14.20  1.5163364.14 22 ∞ 1.00 Image plane ∞ Zoom data Zoom ratio 2.45 WE1 ST1 TE1 WE2ST2 TE2 f 15.50 24.33 37.98 15.42 23.92 35.91 FNO. 4.41 6.93 10.81 4.396.81 10.22 FB 20.00 20.00 20.00 20.00 20.00 20.00 LTL 65.53 65.53 65.5365.53 65.53 65.53 d5 1.60 8.00 13.99 1.60 8.00 13.99 d8 14.00 7.59 1.6114.00 7.59 1.61 d13 2.13 3.46 4.40 2.29 3.88 5.52 d15 5.57 4.24 3.305.41 3.82 2.18 d18 3.30 3.30 3.30 3.30 3.30 3.30 IH 1.92 2.73 3.00 1.922.73 3.00 ω 7.19 6.46 4.43 7.27 6.58 4.47 Unit focal length f1 = 35.13f2 = −13.07 f3 = 12.13 f4 = −12.77 f5 = 22.87

Example 8

Unit mm Surface data Surface no. r d nd νd ER Object plane ∞ ∞  1 50.3581.83 1.57135 52.95 3.8019  2 14.675 1.94 3.5814  3 16.999 1.78 1.8040046.57 3.5442  4 −29.018 0.70 1.69895 30.13 3.4172  5 70.056 Variable  6−39.988 0.70 1.88300 40.76 3.3325  7 14.043 1.76 1.84666 23.78 3.4295  862.753 Variable 3.5483  9 79.109 2.42 1.88300 40.76 7.6446 10 −38.9110.30 7.7223 11 28.814 4.00 1.69680 55.53 7.5858 12 −21.528 0.70 2.0033028.27 7.3319 13 −390.775 0.30 7.2042 14 16.073 0.80 1.72825 28.46 6.907515 10.936 3.78 1.48749 70.23 6.5115 16 −173.628 Variable 6.1797 17−50.070 0.70 1.54814 45.79 5.1843 18 10.428 Variable 4.7986 19 1839.5113.03 1.49700 81.61 4.7871 20 −14.622 0.30 4.7816 21 14.953 3.57 1.8010034.97 4.4519 22 −8.710 0.70 1.74400 44.78 3.9885 23 −31.819 0.56 3.590324 −21.100 1.00 2.00330 28.27 3.2453 25 −20.588 0.31 3.0496 26 −18.7151.00 1.84666 23.78 2.8381 27 12.652 Variable 2.5147 28 ∞ 1.00 1.5211366.54 29 ∞ 0.50 30 ∞ 0.70 1.51633 64.14 31 ∞ 0.50 Image plane ∞ Zoomdata Zoom ratio 1.97 WE1 ST1 TE1 WE2 ST2 TE2 f 15.79 21.34 31.14 15.5020.58 28.60 FNO. 2.42 3.26 4.76 2.37 3.15 4.38 FB 3.39 3.39 3.39 3.393.39 3.39 LTL 64.75 64.75 64.75 64.75 64.75 64.75 d5 0.68 9.03 19.440.68 9.03 19.44 d8 19.56 11.21 0.80 19.56 11.21 0.80 d16 2.95 3.41 3.533.30 4.06 5.02 d18 5.98 5.52 5.40 5.64 4.87 3.91 d27 0.69 0.69 0.69 0.690.69 0.69 IH 1.92 2.73 3.00 1.92 2.73 3.00 ω 7.01 7.33 5.37 7.18 7.605.58 Unit focal length f1 = 63.55 f2 = −25.88 f3 = 14.54 f4 = −15.60 f5= 24.66

Example 9

Unit mm Surface data Surface no. r d nd νd ER Object plane ∞ ∞  1 97.8961.37 1.69895 30.13 3.1746  2 15.202 2.03 3.0305  3 16.965 1.72 1.6968055.53 3.0133  4 52.126 1.32 1.88300 40.76 2.8922  5 −115.435 Variable  6−32.291 0.70 1.71999 50.23 2.8547  7 10.846 1.59 1.80518 25.42 2.9563  827.963 Variable 3.042  9 50.985 3.00 1.88300 40.76 6.6735 10 −52.8560.30 6.7707 11 17.820 4.00 1.69680 55.53 6.7128 12 −22.230 0.70 1.8051825.42 6.3974 13 129.859 0.50 6.1327 14 9.526 1.05 2.00330 28.27 5.620815 6.583 2.37 1.49700 81.61 4.946 16 9.602 Variable 4.5772 17 −65.3680.70 1.88300 40.76 4.3026 18 38.537 Variable 4.2419 19 15.191 3.891.88300 40.76 4.1943 20 −8.424 0.71 1.69895 30.13 3.8693 21 −120.9581.78 3.518 22 −10.009 0.70 1.60300 65.44 2.9368 23 −39.319 Variable2.8197 24 ∞ 1.00 1.52113 66.54 25 ∞ 0.50 26 ∞ 0.70 1.51633 64.14 27 ∞0.50 Image plane ∞ Zoom data Zoom ratio 1.97 WE1 ST1 TE1 WE2 ST2 TE2 f14.82 20.01 29.23 14.73 19.76 28.07 FNO. 2.82 3.80 5.56 2.80 3.76 5.34FB 4.4 4.4 4.4 4.4 4.4 4.4 LTL 58.97 58.97 58.97 58.97 58.97 58.97 d50.80 6.52 13.32 0.80 6.52 13.32 d8 16.97 10.07 1.70 16.97 10.07 1.70 d162.94 4.12 5.69 3.65 5.44 8.72 d18 5.43 5.43 5.43 4.72 4.11 2.40 d23 1.701.70 1.70 1.70 1.70 1.70 IH 1.92 2.73 3.00 1.92 2.73 3.00 ω 7.48 7.845.81 7.59 7.98 5.90 Unit focal length f1 = 57.42 f2 = −22.84 f3 = 16.10f4 = −27.21 f5 = 19.70

Next, the values of conditional expressions (2) to (13) in each exampleare shown below.

Conditional expression Example 1 Example 2 Example 3 (2) f₄/f₅ −0.71−0.81 −0.75 (3) |β_(ctw)| 1.79 1.33 1.34 (4) d_(ng)/d_(pg) 0.34 0.190.20 (5) φ_(fc)/φ_(L1) 1.76 1.66 1.37 (6) f₄/f_(Lw) −1.00 −0.90 −0.91(7) f₅/f_(Lw) 1.40 1.11 1.21 (8) f_(ng)/f_(pg) −1.19 −1.45 −1.74 (9)|β_(ctt)|/|β_(ctw)| 0.98 0.97 0.98 (10) φ_(L1)/f_(Lt) 0.07 0.11 0.12(11) (r_(4Gff) + r_(4Gfb))/(r_(4Gff) − r_(4Gfb)) 0.29 0.68 0.92 (12)(r_(lf) + r_(lb))/(r_(lf) − r_(lb)) −1.15 −0.51 0.09 (13) |(y_(w7d′) −y_(w7d))/P|/(1/N) 75.02 105.18 152.38 Conditional expression Example 4Example 5 Example 6 (2) f₄/f₅ −0.67 −0.72 −0.71 (3) |β_(ctw)| 1.18 1.681.58 (4) d_(ng)/d_(pg) 0.24 0.21 0.19 (5) φ_(fc)/φ_(L1) 1.54 1.71 1.57(6) f₄/f_(Lw) −1.12 −0.82 −0.87 (7) f₅/f_(Lw) 1.68 1.15 1.23 (8)f_(ng)/f_(pg) −1.68 −1.56 −1.64 (9) |β_(ctt)|/|β_(ctw)| 0.94 0.96 0.97(10) φ_(L1)/f_(Lt) 0.12 0.11 0.10 (11) (r_(4Gff) + r_(4Gfb))/(r_(4Gff) −r_(4Gfb)) 1.72 0.45 0.83 (12) (r_(lf) + r_(lb))/(r_(lf) − r_(lb)) 0.50−1.23 1.70 (13) |(y_(w7d′) − y_(w7d))/P|/(1/N) 144.29 109.78 186.46Conditional expression Example 7 Example 8 Example 9 (2) f₄/f₅ −0.56−0.63 −1.38 (3) |β_(ctw)| 2.86 1.38 0.60 (4) d_(ng)/d_(pg) 0.22 0.200.19 (5) φ_(fc)/φ_(L1) 1.96 1.36 1.36 (6) f₄/f_(Lw) −0.82 −0.99 −1.84(7) f₅/f_(Lw) 1.48 1.56 1.33 (8) f_(ng)/f_(pg) −1.08 −1.78 −1.42 (9)|β_(ctt)|/|β_(ctw)| 0.93 0.97 1.00 (10) φ_(L1)/f_(Lt) 0.06 0.12 0.11(11) (r_(4Gff) + r_(4Gfb))/(r_(4Gff) − r_(4Gfb)) 0.33 0.66 0.26 (12)(r_(lf) + r_(lb))/(r_(lf) − r_(lb)) −1.52 0.19 −1.68 (13) |(y_(w7d′) −y_(w7d))/P|/(1/N) 86.76 162.91 121.79

As to how the zoom image pickup apparatus of the present embodiment isconnected to an optical instrument is shown in FIG. 20. FIG. 20 shows acase in which an optical instrument is a rigid endoscope.

A rigid endoscope 10 includes a scope-side light guide 1, an objectivelens 2, a relay lens 3, an eyepiece 4, and an optical element 5. Theeyepiece 4 is disposed in an eyepiece portion 6 of the rigid endoscope10. Moreover, a light-source apparatus 8 is connected to the rigidendoscope 10 via a light guiding cable 7.

Light emerged from the light-source apparatus 8 is transmitted up to anincidence portion of the scope-side light guide 1 by the light guidingcable 7. Here, the light guiding cable 7 and the scope-side light guide1 are either connected directly or connected via the optical element 5.The optical element 5 is an element which converts an NA of lightemerged from the light guiding cable 7.

Illumination light incident on the scope-side light guide 1 istransmitted to a front end of the rigid endoscope 10. The Illuminationlight is radiated to an object from the front end of the rigid endoscope10.

An object image I₁ is formed by the objective lens 2. The object imageI₁ is relayed by the relay lens 3, and an object image I₂ is formed at apredetermined position. A user is capable of observing visually theobject through the eyepiece portion 6.

In a case of acquiring an image of an object, a zoom image pickupapparatus 20 of the present embodiment is to be connected to theeyepiece portion 6. The zoom image pickup apparatus 20 includes a mountportion 21, a zoom lens 22, and an image pickup element 23. In FIG. 20,the zoom lens according to the example 1 is used for the zoom lens 22.Since the zoom lens according to the example 1 is an optical systemsuitable for a type in which image pickup is carried out by using threeimage pickup elements (three-plate type), a prism is disposed prior tothe image pickup element 23. By using the zoom lens of another example,it is possible to use a type in which image pickup is carried out byusing one image pickup element (single-plate type).

As the mount portion 21, amount such as amount of screw type and a mountof bayonet type is to be used. Even for the eyepiece portion 6, by usinga mount such as the mount of screw type and the mount of bayonate type,it is possible to connect the rigid endoscope 10 and the image pickupapparatus 20.

By the rigid endoscope 10 and the zoom image pickup apparatus 20 beingconnected, light from an object is incident from the eyepiece lens 4 tothe zoom lens 22 via the mount portion 21. The light incident on thezoom lens 22 is formed as an image by the zoom lens 22, and an image ofthe object is formed at an image forming position. The image pickupelement 23 being disposed at the image forming position, the objectimage is picked up by the image pickup element 23. In such manner, it ispossible to acquire an image of the object.

The image of the object is sent to a processing unit 30. In theprocessing unit 30, various processing is carried out according to therequirement. The image of the object is eventually displayed on atelevision monitor 31.

In the display of the image of the object, as shown in FIG. 20, anarrangement may be made such that a side corresponding to an upperportion of the unit, of a peripheral portion of an image observedbecomes a caved-in image. For this, a projection may be provided to apart of an aperture of a field stop of the rigid endoscope. When such anarrangement is made, a relationship of an image achieved by light rayspassing through the eyepiece portion and the upper portion of the unitbecomes easily understandable.

By devising a method for disposing a fiber bundle in a case of aflexible endoscope, it is possible to achieve similar effect. Moreover,in a telescope and a microscope, it is preferable to use a field stophaving a similar shape. By disposing the bundle, an arrangement may bemade such that a side corresponding to an upper portion of the unit, ofa peripheral portion of an image observed becomes caved-in image. Arelationship of an image achieved by light rays passing through theeyepiece portion and the upper portion of the unit becomes easilyunderstandable.

The size of the object image I₂ is determined by the objective lens 2and the relay lens 3. Therefore, in the zoom image pickup apparatus 20,an image of a predetermined size is formed on the image pickup element23 by the zoom lens 22. Consequently, the size of the image formed onthe image pickup element 23 varies according to the magnification of thezoom lens.

A size of a light receiving surface of the image pickup element beingconstant, in a telescope, an image larger than the light receivingsurface is formed on the light receiving surface of the image pickupelement 23. In this case, since a part of the object image I2 iscaptured, an image in which a part of an object has been enlarged isacquired.

At the wide angle end, on the light receiving surface of the imagepickup element 23, the object image I₂ is formed to be accommodated in alongitudinal width of the light receiving surface. At this time, in ashort-side direction, a peripheral portion of the object image I₂ runsoff the light receiving surface. Consequently, an image displayed on thetelevision monitor 31 has four corners cut, such as an image having aportrait-oriented oval shape as an outer shape.

In this example, the zoom lens according to the present embodiment hasbeen used for the zoom lens 22. Therefore, an image of a size desired bythe user is achieved. In this case, it is possible to achieve an imagein which aberrations are corrected favorably. Furthermore, the variationin the image height being small at the time of focusing, it is possibleto achieve an image with no uncomfortable feeling all the time.

According to the present invention, it is possible to provide a zoomimage pickup apparatus in which an occurrence of axial aberration issuppressed adequately, and the fluctuation in the spherical aberrationat the time of focusing is small.

As described above, the present invention is suitable for a zoom pickupapparatus in which an occurrence of axial aberration is suppressedadequately, and the fluctuation in the spherical aberration at the timeof focusing is small.

What is claimed is:
 1. A zoom image pickup apparatus, comprising: amount portion; a zoom lens which forms an image of light incident fromthe mount portion; and an image pickup element which is disposed at animage forming position, wherein the zoom lens includes in order from anobject side, a first lens unit having a positive refractive power, asecond lens unit having a negative refractive power, a third lens unithaving a positive refractive power, a fourth lens unit having a negativerefractive power, and a fifth lens unit having a positive refractivepower, and the fourth lens unit is a focusing lens unit, and at the timeof zooming from a wide angle end to a telephoto end, at least the secondlens unit and the fourth lens unit move, and at the wide angle end whenfocused to a first object, the following conditional expression (1) issatisfied:φ_(L1)<φ_(3GL1)  (1) where, φ_(L1) denotes an effective diameter of alens surface positioned nearest to object of the zoom lens, φ_(3GL1)denotes an effective diameter of a lens surface positioned nearest toobject of the third lens unit, the first object is an object when anobject-point distance is 1000 mm, here the object-point distance is adistance from a lens surface positioned nearest to object of the zoomlens, up to the object, and the effective diameter is the maximumdiameter of a range on a target lens surface, through which a light raycontributing to image formation passes.
 2. The zoom image pickupapparatus according to claim 1, wherein the following conditionalexpression (2) is satisfied:−4.5<f ₄ /f ₅<−0.2  (2) where, f₄ denotes a focal length of the fourthlens unit, and f₅ denotes a focal length of the fifth lens unit.
 3. Thezoom image pickup apparatus according to claim 1, wherein the followingconditional expression (3) is satisfied:0.55<|β_(ctw)|<5  (3) where, β_(ctw)=(1−β_(fcw)×β_(fcw))×β_(w)′×β_(w)′,here each of β_(fcw) and β_(w)′ is a lateral magnification at the wideangle end when focused to the first object, and β_(fcw) denotes alateral magnification of the fourth lens unit and β_(w)′ denotes alateral magnification of a lens unit positioned on an image side of thefourth lens unit, the first object is an object when the object-pointdistance is 1000 mm, and the object-point distance is a distance from alens surface positioned nearest to object of the zoom lens up to anobject.
 4. The zoom image pickup apparatus according to claim 1, whereinthe following conditional expression (4) is satisfied:0.1<d _(ng) /d _(pg)<0.9  (4) where, each of d_(ng) and d_(pg) is athickness on an optical axis of a lens unit, and d_(ng) denotes athickness of the second lens unit having a negative refractive power,and d_(pg) denotes a thickness of the third lens unit having a positiverefractive power.
 5. The zoom image pickup apparatus according to claim1, wherein the following conditional expression (5) is satisfied:1<φ_(fc)/φ_(L1)<3  (5) where, each of φ_(fc) and φ_(L1) is an effectivediameter at the wide angle end when focused to the first object, andφ_(fc) denotes an effective diameter of a lens surface positionednearest to object of the focusing lens unit, φ_(L1) denotes theeffective diameter of a lens surface positioned nearest to object of thezoom lens, the first object is an object when an object-point distanceis 1000 mm, where the object-point distance is the distance from thelens surface positioned nearest to object of the zoom lens, up to theobject, and the effective diameter is the maximum diameter of a range ona target lens surface, through which a light ray contributing to imageformation passes.
 6. The zoom image pickup apparatus according to claim1, wherein the following conditional expression (6) is satisfied:−4<f ₄ /f _(Lw)<−0.4  (6) where, f₄ denotes a focal length of the fourthlens unit, f_(Lw) denotes a focal length at the wide angle end of thezoom lens when focused to the first object, the first object is anobject when an object-point distance is 1000 mm, and the object-pointdistance is a distance from a lens surface positioned nearest to objectof the zoom lens up to the object.
 7. The zoom image pickup apparatusaccording to claim 1, wherein the following conditional expression (7)is satisfied1<f ₅ /f _(Lw)<3  (7) where, f₅ denotes a focal length of the fifth lensunit, f_(Lw) denotes a focal length at a wide angle end of the zoom lenswhen focused to the first object, and the first object is an object whenan object-point distance is 1000 mm, here the object-point distance is adistance from a lens surface positioned nearest to object of the zoomlens, up to the object.
 8. The zoom image pickup apparatus according toclaim 1, wherein the following conditional expression (8) is satisfied:−5<f _(ng) /f _(pg)<−0.5  (8) where, f_(ng) denotes a focal length of alens having the largest negative refractive power from among focallengths of lens units positioned on the object side of the fourth lensunit, and f_(pg) denotes a focal length of a lens having the largestpositive refractive power from among focal lengths of lens unitspositioned on the object side of the fourth lens unit.
 9. The zoom imagepickup apparatus according to claim 1, wherein only the fourth lens unitmoves at the time of focusing, and the following conditional expression(9) is satisfied0.8<|β_(ctt)|/|β_(ctw)|<1.8  (9) where,β_(ctt)=(1−β_(fct)×β_(fct))×β_(t)′×β_(t)′β_(ctw)=(1−β_(fcw)×β_(fcw))×β_(w)′×β_(w)′, here each of β_(fct) andβ_(t)′ is a lateral magnification at the telephoto end when focused tothe first object, and α_(fct) denotes a lateral magnification of thefourth lens unit and β_(t)′ denotes a lateral magnification of a lensunit positioned on an image side of the fourth lens unit, each ofβ_(fcw) and β_(w)′ is a lateral magnification at the wide angle end whenfocused to the first object, and β_(fcw) denotes a lateral magnificationof the fourth lens unit and β_(w)′ denotes a lateral magnification of alens unit positioned on an image side of the fourth lens unit, and thefirst object is an object when the object-point distance is 1000 mm, andthe object-point distance is a distance from a lens surface positionednearest to object of the zoom lens up to an object.
 10. The zoom imagepickup apparatus according to claim 1, wherein the following conditionalexpression (10) is satisfied:0.03<θ_(L1) /f _(Lt)<0.2  (10) where, φ_(L1) is the effective diameterof a lens surface positioned nearest to object of the zoom lens, anddenotes an effective diameter at the wide angle end when focused to thefirst object, f_(Lt) denotes a focal length at the telephoto end of thezoom lens when focused to the first object, the first object is anobject when an object-point distance is 1000 mm, where the object-pointdistance is the distance from the lens surface positioned nearest toobject of the zoom lens, up to the object, and the effective diameter isthe maximum diameter of a range on a target lens surface, through whicha light ray contributing to image formation passes.
 11. The zoom imagepickup apparatus according to claim 1, wherein at the time of zoomingfrom the wide angle end to the telephoto end, only the second lens unitand the fourth lens unit move, and the first lens unit, the third lensunit, and the fifth lens unit are fixed.
 12. The zoom image pickupapparatus according to claim 1, wherein the third lens unit includes apositive lens which is disposed nearest to object and a cemented lenswhich is disposed nearest to image.
 13. The zoom image pickup apparatusaccording to claim 1, wherein a rearmost lens is disposed nearest toimage, and the rearmost lens includes a positive lens which is disposednearest to object and a negative lens which is disposed nearest toimage.
 14. The zoom image pickup apparatus according to claim 1, whereinthe following conditional expression (11) is satisfied:−5<(r _(4Gff) r _(4Gfb))r _(4Gff) r _(4Gfb))<5  (11) where, r_(4Gff)denotes a radius of curvature of an object-side lens surface of a lenspositioned nearest to object in the fourth lens unit, and r_(4Gfb)denotes a radius of curvature of an image-side lens surface of a lenspositioned nearest to image in the fourth lens unit.
 15. The zoom imagepickup apparatus according to claim 1, wherein the following conditionalexpression (12) is satisfied:−5<(r _(1f) +r _(1b))/(r _(1f) −r _(1b))<5  (12) where, r_(1f) denotes aradius of curvature of an object-side lens surface of a lens positionednearest to image, and r_(1b) denotes a radius of curvature of animage-side lens surface of the lens positioned nearest to image.
 16. Azoom image pickup apparatus, comprising: a mount portion; a zoom lenswhich forms an image of light incident from the mount portion; and animage pickup element which is disposed at an image forming position,wherein the zoom lens includes in order from an object side, a firstlens unit having a positive refractive power, a second lens unit havinga negative refractive power, a third lens unit having a positiverefractive power, a fourth lens unit having a negative refractive power,and a fifth lens unit having a positive refractive power, and the fourthlens unit is a focusing lens unit, and at the time of zooming from awide angle end to a telephoto end, only the second lens unit and thefourth lens unit move, and the first lens unit, the third lens unit, andthe fifth lens unit are fixed, and the following conditional expression(13) is satisfied:|(y _(w7d′) −y _(w7d))/P|/(1/N)<250  (13) where, a side of the mountportion is let to be an object side and a side of the image pickupelement is let to be an image side, each of y_(w7d) and y_(w7d′) is aheight of a predetermined light ray at a position at which thepredetermined light ray intersects an image plane, and y_(w7d) denotes alight-ray height when focused to the first object and y_(w7d′) denotes alight-ray height in a defocused state, here the defocused state is astate in which the focusing lens unit is moved by Δ_(s2) when focused tothe first object, and Δ_(s2)=10×P,0.0008<P<0.005,0.05<1/N<1, where, N denotes the number of pixels (unitmillions of pixels) of the image pickup element, P denotes a pixel pitch(unit mm) of the image pickup element, the predetermined light ray is alight ray with an angle of view of 7 degrees at the wide angle end,which passes through a center of a lens surface nearest to object of thezoom lens, the first object is an object when an object-point distanceis 1000 mm, and the object-point distance is a distance from a lenssurface positioned nearest to object of the zoom lens, up to the object.